C H A P T E R

5

Creating and Maintaining VLANs
A virtual LAN (VLAN) is a switched network that is logically segmented by function, project team, or application, without regard to the physical locations of the users. Any switch port can belong to a VLAN, and unicast, broadcast, and multicast packets are forwarded and flooded only to stations in the VLAN. Each VLAN is considered a logical network, and packets destined for stations that do not belong to the VLAN must be forwarded through a router or bridge as shown in Figure 5-1. Because a VLAN is considered a separate logical network, it contains its own bridge Management Information Base (MIB) information and can support its own implementation of the Spanning Tree Protocol (STP). This chapter describes how to create and maintain VLANs through the Cluster Management software and the command-line interface (CLI). It contains the following information:

How to configure static-access and multi-VLAN ports without having the VLAN Trunk Protocol (VTP) database globally propagate VLAN configuration information. How VTP works and how to configure its domain name, modes, version, and pruning capability. How to add, modify, and remove VLANs with different media characteristics to and from the VTP database. How to configure Fast Ethernet and Gigabit Ethernet VLAN trunks on a switch. The switch supports Inter-Switch Link (ISL) and IEEE 802.1Q trunking methods of transmitting VLAN traffic. This section describes how to configure the allowed-VLAN list, the pruning-eligible list, and the native VLAN for untagged traffic. Two methods of load sharing using STP are also described.

• • •

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How to configure dynamic port VLAN membership by using the VLAN Membership Policy Server (VMPS). The VMPS dynamically assigns switch ports to VLANs based on the source Media Access Control (MAC) address of the end station connected to the port. When you move an end station from a port on one switch in the network to a port on another switch in the network, that switch dynamically assigns the new port to the proper VLAN for that end station. How to configure IEEE 802.1p class of service (CoS) port priorities for port forwarding untagged frames. You assign CoS to certain types of traffic to give it priority over other traffic.
VLANs as Logically Defined Networks
Catalyst 3500 series XL Engineering VLAN Marketing VLAN Accounting VLAN

Figure 5-1

Cisco router

Floor 3 Catalyst 2900 series XL Fast Ethernet

Floor 2 Catalyst 2900 series XL

Floor 1
15933

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Creating and Maintaining VLANs Number of Supported VLANs

Number of Supported VLANs
Table 5-1 lists the number of supported VLANs on 2900 and 3500 XL switches.
Table 5-1 Number of Supported VLANs

Catalyst Switch 2900 XL modular switches with 8 MB of DRAM 3500 XL switches

Number of Supported VLANs 250 250

Trunking Supported? Yes Yes Yes

2900 XL fixed switches with 8 MB of DRAM 64

VLANs are identified with a number between 1 and 1001. Regardless of the switch model, only 64 possible instances of STP are supported. The switches in Table 5-1 support both Inter-Switch Link (ISL) and IEEE 802.1Q trunking methods for transmitting VLAN traffic over 100BaseT and Gigabit Ethernet ports. However, trunking is not supported on all switches and modules. For the list of products that support trunking, refer to the Release Notes for Catalyst 2900 Series XL and Catalyst 3500 Series XL Cisco IOS Release 12.0(5)XU.

VLAN Port Membership Modes
You configure a port to belong to a VLAN by assigning a membership mode that determines the kind of traffic the port carries and the number of VLANs it can belong to. Table 5-2 lists the membership modes and characteristics.

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The VLAN ID is then displayed in the Assigned VLANs column of the VLAN Membership window. the switch learns and manages the addresses associated with the port on a per-VLAN basis. all ports are static-access ports assigned to VLAN 1. For more information. A multi-VLAN port can belong to up to 250 VLANs (some models only support 64 VLANs) and is manually assigned. and renaming of VLANs on a network-wide basis. Trunk (ISL. By default. you can map the LAN emulation (LANE) client to a VLAN or bind one or more permanent virtual connections (PVCs) to a VLAN.Chapter 5 VLAN Port Membership Modes Creating and Maintaining VLANs Table 5-2 Port Membership Modes Membership Mode Static-access Multi-VLAN VLAN Membership Characteristics A static-access port can belong to one VLAN and is manually assigned. The VMPS can be a Catalyst 5000 series switch but never a 2900 or 3500 XL switch. deletion. You cannot configure a multi-VLAN port when a trunk is configured on the switch. You can also modify the pruning-eligible list to block flooded traffic to VLANs on trunk ports that are included in the list. A trunk is a member of all VLANs in the VLAN database by default. For more information.1Q) Note By using the ATM module CLI. An ATM port can only be a trunk port. but membership can be limited by configuring the allowed-VLAN list. VTP exchanges VLAN configuration messages with other switches over trunk links. When a port belongs to a VLAN. Cisco IOS Desktop Switching Software Configuration Guide 5-4 78-6511-04 . or IEEE 802. see the “Managing the MAC Address Tables” section on page 4-42. refer to the Catalyst 2900 Series XL ATM Modules Installation and Configuration Guide. Dynamic access A dynamic-access port can belong to one VLAN and is dynamically assigned by a VMPS. VLAN traffic on the multi-VLAN port is not encapsulated. VTP maintains VLAN configuration consistency by managing the addition. ATM.

Some restrictions apply to multi-VLAN ports. For more information. see the “Managing Configuration Conflicts” section on page 4-2. You must connect the multi-VLAN port to a router or server. Table 5-3 VLAN Combinations Port Mode VTP Required? Configuration Procedure “Assigning Static-Access Ports to a VLAN” section on page 5-7 Comments If you do not want to use VTP to globally propagate the VLAN configuration information. The switch automatically transitions to VTP transparent mode (VTP is disabled). No VTP configuration is required.Chapter 5 Creating and Maintaining VLANs VLAN Port Membership Modes VLAN Membership Combinations You can configure your switch ports in various VLAN membership combinations as listed in Table 5-3. you can assign a static-access port to a VLAN and set the VTP mode to transparent to disable VTP. Static-access ports No Static-access and No multi-VLAN ports “Overlapping VLANs and Multi-VLAN Ports” section on page 5-9 “Assigning Static-Access Ports to a VLAN” section on page 5-7 Cisco IOS Desktop Switching Software Configuration Guide 78-6511-04 5-5 .

change the pruning-eligible list.Chapter 5 VLAN Port Membership Modes Creating and Maintaining VLANs Table 5-3 VLAN Combinations (continued) Port Mode Static-access and trunk ports VTP Required? Recommended Configuration Procedure “CLI: Configuring VTP Server Mode” section on page 5-21 Add. Some restrictions apply to trunk ports. Configure the VMPS and the client with the same VTP domain name. or remove VLANs in the database as described in the “Configuring VLANs in the VTP Database” section on page 5-32 “CLI: Assigning Static-Access Ports to a VLAN” section on page 5-37 Comments Make sure to configure at least one trunk port on the switch and that this trunk port is connected to the trunk port of a second switch. You can define the allowed-VLAN list. modify. Dynamic-access and trunk ports Yes “CLI: Entering the IP Address of the VMPS” section on page 5-63 “CLI: Configuring Dynamic Ports on VMPS Clients” section on page 5-64 “Configuring a Trunk Port” section on page 5-40 so that the VMPS client can receive VTP information from the VMPS You must connect the dynamic-access port to an end station and not to another switch. You can change the VTP version on the switch and enable VTP pruning. For more information. see the “Trunks Interacting with Other Features” section on page 5-39. Cisco IOS Desktop Switching Software Configuration Guide 5-6 78-6511-04 . and configure the native VLAN for untagged traffic on the trunk port. change the pruning-eligible list. You can define the allowed-VLAN list. and configure the native “Configuring a Trunk Port” section on page 5-40 VLAN for untagged traffic on the trunk port. You can change the reconfirmation interval and the retry count on the VMPS client switch.

and IOS commands operate as usual. Once you have accessed the member switch. see the “Changing the Management VLAN” section on page 3-33. For more information about the rcommand command. the management VLAN is VLAN 1. and candidate switches must be through ports that belong to the management VLAN. cluster members. and the Management VLAN This software release supports the grouping of switches into a cluster that can be managed as a single entity. The command switch is the single point of management for the cluster and cluster members. For information on configuring the management VLAN.Chapter 5 Creating and Maintaining VLANs Assigning Static-Access Ports to a VLAN Clusters. Assigning Static-Access Ports to a VLAN By default. When configuring port parameters. Links among a command switch. To assign a VLAN. for example. all ports are static-access ports assigned to the management VLAN. Cisco IOS Desktop Switching Software Configuration Guide 78-6511-04 5-7 . command mode changes. If you are configuring VLANs on a member switch. refer to the Cisco IOS Desktop Switching Command Reference (online only). you can use the privileged EXEC rcommand command and the number of the member switch to display the member-switch CLI. By default. ensure that the port through which you are connected to a switch is in the management VLAN. If you are using SNMP or the Cluster Management Suite (CMS) to manage the switch. Enter exit on the member switch in privileged EXEC mode to return to the command-switch CLI. VLAN 1. You can assign a static-access port to a VLAN without having VTP globally propagate VLAN configuration information (VTP is disabled). you might need to enter an extra command from the command-switch CLI to access the member switch. VLAN Membership. you access the VLAN Membership window (Figure 5-2) by selecting VLAN>VLAN Membership from the menu bar and clicking the Assign VLANs tab.

command. which disables VTP. by selecting VLAN>VTP Management from the menu bar and clicking the VTP Configuration tab (Figure 5-5). If you are assigning a port on a cluster member switch to a VLAN. refer to the Cisco IOS Desktop Switching Command Reference (online only). You can also assign the port through the CLI on standalone.Chapter 5 Assigning Static-Access Ports to a VLAN Creating and Maintaining VLANs Figure 5-2 VLAN Membership: Assign VLANs Tab Display the VLANs configured on a switch and the ports and membership mode of a given VLAN. For more information on how to use this command. Cisco IOS Desktop Switching Software Configuration Guide 5-8 29678 78-6511-04 . and member switches. You configure the switch for VTP transparent mode. first log in to the member switch by using the privileged EXEC rcommand command.

Configuring a switch port for multi-VLAN mode causes VTP to transition to transparent mode. all the VLANs to which the port belongs learn the address. Multi-VLAN ports also respond to the STP messages generated by the different instances of STP in each VLAN. Enter the VLAN membership mode for multi-VLAN ports. Overlapping VLANs and Multi-VLAN Ports A multi-VLAN port connected to a router can link two or more VLANs. follow these steps to assign ports for multi-VLAN membership: Command Step 1 Step 2 Step 3 Step 4 Purpose Enter global configuration mode. configure terminal interface interface switchport mode multi switchport multi vlan vlan-list Step 5 Step 6 end show interface interface-id switchport Return to privileged EXEC mode.Chapter 5 Creating and Maintaining VLANs Overlapping VLANs and Multi-VLAN Ports Beginning in privileged EXEC mode. Separate nonconsecutive VLAN IDs with a comma. use a hyphen to designate a range of IDs. A multi-VLAN port performs normal switching functions in all its assigned VLANs. and enter the port to be added to the VLAN. which disables VTP. Enter interface configuration mode. Intra-VLAN traffic stays within the boundaries of the respective VLANs as shown in Figure 5-3. Cisco IOS Desktop Switching Software Configuration Guide 78-6511-04 5-9 . Verify your entries. For example. when a multi-VLAN port receives an unknown MAC address. Connectivity between VLANs is accomplished by using the router connected to the multi-VLAN port. The “Finding More Information About IOS Commands” section on page 4-1 contains the path to the complete IOS documentation. Assign the port to more than one VLAN.

To display this window. select VLAN>VLAN Membership from the menu bar. first log into the member switch by using the privileged EXEC rcommand command. You can assign a multi-VLAN port to VLANs by using the VLAN Management window (Figure 5-2). Cisco IOS Desktop Switching Software Configuration Guide 5-10 12516 VLAN 77 Cisco router VLAN 42 78-6511-04 . and member switches. You can also configure the multi-VLAN port through the CLI on standalone. Figure 5-3 Two VLANs Sharing a Port Connected to a Router Ports in static-access mode Port in multi-VLAN mode Caution To avoid unpredictable STP behavior and a loss of connectivity. Connect multi-VLAN ports to routers or servers. and click the Assign VLANs tab. command.Chapter 5 Overlapping VLANs and Multi-VLAN Ports Creating and Maintaining VLANs For the restrictions that apply to multi-VLAN ports. If you are assigning a port on a cluster member switch to a VLAN. do not connect multi-VLAN ports to hubs or switches. refer to the Cisco IOS Desktop Switching Command Reference (online only). see the “Managing Configuration Conflicts” section on page 4-2. For more information on how to use this command.

Enter the VLAN membership mode for multi-VLAN ports. use a hyphen to designate a range of IDs. configure terminal interface interface switchport mode multi switchport multi vlan vlan-list Step 5 Step 6 end show interface interface-id switchport Return to privileged EXEC mode. follow these steps to assign ports for multi-VLAN membership: Command Step 1 Step 2 Step 3 Step 4 Purpose Enter global configuration mode. Cisco IOS Desktop Switching Software Configuration Guide 78-6511-04 5-11 . Separate nonconsecutive VLAN IDs with a comma. Assign the port to more than one VLAN. which disables VTP. and enter the port to be added to the VLAN. incorrect VLAN-type specifications. such as duplicate VLAN names. and security violations.Chapter 5 Creating and Maintaining VLANs Using the VLAN Trunk Protocol Beginning in privileged EXEC mode. Enter interface configuration mode. Using the VLAN Trunk Protocol VTP is a Layer 2 messaging protocol that maintains VLAN configuration consistency by managing the addition. deletion. Configuring a switch port for multi-VLAN mode causes VTP to transition to transparent mode. Verify your entries. and renaming of VLANs on a network-wide basis. The “Finding More Information About IOS Commands” section on page 4-1 contains the path to the complete IOS documentation. VTP minimizes misconfigurations and configuration inconsistencies that can cause several problems.

or Simple Network Management Protocol (SNMP). If you configure a switch for VTP transparent mode. and they affect only the individual switch. you can create and modify VLANs. By default. Using VTP. Cluster Management software. Cisco IOS Desktop Switching Software Configuration Guide 5-12 78-6511-04 . If the switch receives a VTP advertisement over a trunk link. including Inter-Switch Link (ISL). see the “Domain Names” section on page 5-16. The VTP Domain A VTP domain (also called a VLAN management domain) consists of one switch or several interconnected switches under the same administrative responsibility. a 2900 or 3500 XL switch is in the no-management-domain state until it receives an advertisement for a domain over a trunk link (a link that carries the traffic of multiple VLANs) or until you configure a domain name. and Asynchronous Transfer Mode (ATM) LAN Emulation (LANE). but VLAN information is not propagated over the network until a domain name is specified or learned. you must decide whether to use VTP in your network. it inherits the domain name and configuration revision number.1Q. you cannot send information about VLANs to other switches. VTP advertisements are sent over all trunk connections. IEEE 802. such as a 2900 or 3500 XL switch. The default VTP mode is server mode. you can make configuration changes centrally on a single switch.10. For domain name and password configuration guidelines.Chapter 5 Using the VLAN Trunk Protocol Creating and Maintaining VLANs Before you create VLANs. the change is propagated to all switches in the VTP domain. and have those changes automatically communicated to all the other switches in the network. The switch then ignores advertisements with a different domain name or an earlier configuration revision number. but the changes are not transmitted to other switches in the domain. A switch can be in only one VTP domain. IEEE 802. Without VTP. When you make a change to the VLAN configuration on a VTP server. You make global VLAN configuration changes for the domain by using the CLI.

In VTP transparent mode. transparent switches do forward VTP advertisements that they receive from other switches. You can create. Two configurations can cause a switch to automatically change its VTP mode: • When the network is configured with more than 64 VLANs. In VTP client mode. but they are not advertised to other switches. the switch automatically changes from VTP server or client mode to VTP transparent mode.Chapter 5 Creating and Maintaining VLANs Using the VLAN Trunk Protocol VTP Modes and VTP Mode Transitions You can configure a supported switch to be in one of the VTP modes listed in Table 5-4: Table 5-4 VTP Modes VTP Mode VTP server Description In this mode. you can create. VLAN configurations are saved in nonvolatile RAM. a VTP client behaves like a VTP server. transparent A VTP transparent switch does not advertise its VLAN configuration and does not synchronize its VLAN configuration based on received advertisements. and delete VLANs and specify other configuration parameters (such as VTP version) for the entire VTP domain. VTP client In this mode. VTP server is the default mode. In VTP server mode. VTP servers advertise their VLAN configurations to other switches in the same VTP domain and synchronize their VLAN configurations with other switches based on advertisements received over trunk links. VTP transparent switches do not participate in VTP. VTP In this mode. modify. modify. VLAN configurations are saved in nonvolatile RAM. VLAN configurations are not saved in nonvolatile RAM. but you cannot create. change. However. or delete VLANs on a VTP client. Cisco IOS Desktop Switching Software Configuration Guide 78-6511-04 5-13 . and delete VLANs on a switch in VTP transparent mode. The switch then operates with the VLAN configuration that preceded the one that sent it into transparent mode.

Neighboring switches receive these advertisements and update their VTP and VLAN configurations as necessary. VTP advertisements distribute the following global domain information in VTP advertisements: • • • • VTP domain name VTP configuration revision number Update identity and update timestamp MD5 digest VTP advertisements distribute the following VLAN information for each configured VLAN: • • • • • VLAN ID VLAN name VLAN type VLAN state Additional VLAN configuration information specific to the VLAN type Cisco IOS Desktop Switching Software Configuration Guide 5-14 78-6511-04 . you must ensure that at least one trunk port is configured on the switch and that this trunk port is connected to the trunk port of a second switch. the switch cannot receive any VTP advertisements. the switch automatically changes to transparent mode. Note Because trunk ports send and receive VTP advertisements. Otherwise. VTP Advertisements Each switch in the VTP domain sends periodic global configuration advertisements from each trunk port to a reserved multicast address.Chapter 5 Using the VLAN Trunk Protocol Creating and Maintaining VLANs • When a multi-VLAN port is configured on a supported switch in VTP server mode or client mode. The “VTP Configuration Guidelines” section on page 5-16 provides tips and caveats for configuring VTP.

Consistency checks are not performed when new information is obtained from a VTP message or when information is read from nonvolatile RAM. VTP version 2 forwards VTP messages in transparent mode without checking the version and domain name. Only VLANs included in the pruning-eligible list can be pruned. The unrecognized TLV is saved in nonvolatile RAM when the switch is operating in VTP server mode. For more information about Token Ring VLANs. VTP pruning blocks unneeded flooded traffic to VLANs on trunk ports that are included in the pruning-eligible list.Chapter 5 Creating and Maintaining VLANs Using the VLAN Trunk Protocol VTP Version 2 VTP version 2 supports the following features not supported in version 1: • Token Ring support—VTP version 2 supports Token Ring LAN switching and VLANs (Token Ring Bridge Relay Function [TrBRF] and Token Ring Concentrator Relay Function [TrCRF]). If the digest on a received VTP message is correct. Because only one domain is supported. a VTP transparent switch inspects VTP messages for the domain name and version and forwards a message only if the version and domain name match. and unknown unicast traffic across all trunk links within a VTP domain even though receiving switches might discard them. Version-Dependent Transparent Mode—In VTP version 1. see the “VLANs in the VTP Database” section on page 5-27. Consistency Checks—In VTP version 2. a switch floods broadcast. the Cluster Management software. By default. Unrecognized Type-Length-Value (TLV) support—A VTP server or client propagates configuration changes to its other trunks. its information is accepted without consistency checks. Without VTP pruning. VLAN consistency checks (such as VLAN names and values) are performed only when you enter new information through the CLI. VLANs 2 through 1001 are Cisco IOS Desktop Switching Software Configuration Guide 78-6511-04 5-15 . or SNMP. multicast. • • • VTP Pruning Pruning increases available bandwidth by restricting flooded traffic to those trunk links that the traffic must use to reach the destination devices. even for TLVs it is not able to parse.

all switches in the VTP domain must be configured with the same domain name. and the VTP version number. In addition. If the VLANs are configured as pruning-ineligible. you must always assign a domain name. Figure 5-4 Optimized Flooded Traffic with VTP Pruning Switch 4 Port 2 Flooded traffic is pruned. Port 4 Catalyst 2900 XL or Catalyst 3500 XL Switch 2 Red VLAN Switch 5 Flooded traffic is pruned. Domain Names When configuring VTP for the first time. Port 5 Port 1 30768 Switch 6 Switch 3 Switch 1 VTP Configuration Guidelines The following sections describe the guidelines you should follow when configuring the VTP domain name and password. Figure 5-4 shows a switched network with VTP pruning enabled. The broadcast traffic from Switch 1 is not forwarded to Switches 3. VTP pruning is also supported with VTP version 1 and version 2.Chapter 5 Using the VLAN Trunk Protocol Creating and Maintaining VLANs pruning eligible on 2900 and 3500 XL trunk ports. 5. Switches in VTP transparent mode do not exchange VTP messages with other switches. Cisco IOS Desktop Switching Software Configuration Guide 5-16 78-6511-04 . the flooding continues. and you do not need to configure a VTP domain name for them. and 6 because traffic for the Red VLAN has been pruned on the links indicated (port 5 on Switch 2 and port 4 on Switch 4).

and VTP does not propagate the VLAN configuration to other switches. to a version that does support VTP.Chapter 5 Creating and Maintaining VLANs Using the VLAN Trunk Protocol Caution Do not configure a VTP domain if all switches are operating in VTP client mode. the domain password. If you want the switch to propagate VLAN configuration information to other switches and to learn the VLANs enabled on the network. and VTP enters transparent mode. Caution The domain does not function properly if you do not assign the same password to each switch in the domain. and change the VTP mode to VTP server. it is impossible to make changes to the VLAN configuration of that domain. The domain name becomes UPGRADE. the switch accepts the next VTP advertisement that uses the same password and domain name in the advertisement. If you are adding a new switch to an existing network that has VTP capability. After the configuration. you must configure the switch with the correct domain name. If you configure a VTP password for a domain. All domain switches must share the same password. Therefore. such as Cisco IOS Release 11. the new switch learns the domain name only after the applicable password has been configured on the switch. make sure you configure at least one switch in the VTP domain for VTP server mode. ports that belong to a VLAN retain their VLAN membership. Cisco IOS Desktop Switching Software Configuration Guide 78-6511-04 5-17 .2(8)SA3. Switches without a password or with the wrong password reject VTP advertisements. a 2900 or 3500 XL switch that is booted without a VTP configuration does not accept VTP advertisements until you configure it with the correct password. but it is not required. Passwords You can configure a password for the VTP domain. If you configure the domain. Upgrading from Previous Software Releases When you upgrade from a software version that supports VLANs but does not support VTP.

Chapter 5 Using the VLAN Trunk Protocol

Creating and Maintaining VLANs

VTP Version
Follow these guidelines when deciding which VTP version to implement:
• •

All switches in a VTP domain must run the same VTP version. A VTP version 2-capable switch can operate in the same VTP domain as a switch running VTP version 1 if version 2 is disabled on the version 2-capable switch (version 2 is disabled by default). Do not enable VTP version 2 on a switch unless all of the switches in the same VTP domain are version-2-capable. When you enable version 2 on a switch, all of the version-2-capable switches in the domain enable version 2. If there is a version 1-only switch, it will not exchange VTP information with switches with version 2 enabled. If there are Token Ring networks in your environment (TrBRF and TrCRF), you must enable VTP version 2 for Token Ring VLAN switching to function properly. To run Token Ring and Token Ring-Net, disable VTP version 2. Enabling or disabling VTP pruning on a VTP server enables or disables VTP pruning for the entire VTP domain.

Default VTP Configuration
Table 5-5 shows the default VTP configuration.
Table 5-5 VTP Default Configuration

Feature VTP domain name VTP mode VTP version 2 enable state VTP password VTP pruning

Default Value Null. Server. Version 2 is disabled. None. Disabled.

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Configuring VTP
You can configure VTP by using the VTP Management window (Figure 5-5). To display this window, select VLAN>VTP Management from the menu bar, and click the VTP Configuration tab.
Figure 5-5 VTP Management: VTP Configuration Tab

Read-only VTP information.

Configures VLAN parameters when you add or modify a VLAN in the VTP database.

Assign a VTP domain name from 1 to 32 characters. All switches under the same administrative responsibility must be configured with the same domain name.

If you configure a password, it must be the same on all switches in the domain.

After you configure VTP, you must configure a trunk port so that the switch can send and receive VTP advertisements. For more information, see the “How VLAN Trunks Work” section on page 5-38. You can also configure VTP through the CLI on standalone, command, and member switches by entering commands in the VLAN database command mode. If you are configuring VTP on a cluster member switch to a VLAN, first log in to the member switch by using the privileged EXEC rcommand command. For more information on how to use this command, refer to the Cisco IOS Desktop Switching Command Reference (online only).
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When you enter the exit command in VLAN database mode, it applies all the commands that you entered. VTP messages are sent to other switches in the VTP domain, and you are returned to privileged EXEC mode.

Note

The Cisco IOS end and Ctrl-Z commands are not supported in VLAN database mode.

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vlan database vtp domain domain-name Step 3 vtp password password-value (Optional) Set a password for the VTP domain. In the display. Beginning in privileged EXEC mode. Step 4 Step 5 Step 6 vtp server exit show vtp status Configure the switch for VTP server mode (the default). If you configure a VTP password. The “Finding More Information About IOS Commands” section on page 4-1 contains the path to the complete IOS documentation. you can change the VLAN configuration and have it propagated throughout the network. Configure a VTP administrative-domain name. the VTP domain does not function properly if you do not assign the same password to each switch in the domain. follow these steps to configure the switch for VTP server mode: Command Step 1 Step 2 Purpose Enter VLAN database mode.Chapter 5 Creating and Maintaining VLANs Using the VLAN Trunk Protocol CLI: Configuring VTP Server Mode When a switch is in VTP server mode. All switches operating in VTP server or client mode under the same administrative responsibility must be configured with the same domain name. Verify the VTP configuration. Cisco IOS Desktop Switching Software Configuration Guide 78-6511-04 5-21 . The password can be from 8 to 64 characters. Return to privileged EXEC mode. The name can be from 1 to 32 characters. check the VTP Operating Mode and the VTP Domain Name fields.

check the VTP Operating Mode field. The password can be from 8 to 64 characters. Therefore. The default setting is VTP server. you cannot change its VLAN configuration. Caution Do not configure a VTP domain name if all switches are operating in VTP client mode. All switches operating in VTP server or client mode under the same administrative responsibility must be configured with the same domain name. If you configure a VTP password. it is impossible to make changes to the VLAN configuration of that domain. propagate it throughout the administrative domain. Configure a VTP administrative-domain name. follow these steps to configure the switch for VTP client mode: Command Step 1 Step 2 Step 3 Purpose Enter VLAN database mode. Step 5 Step 6 exit show vtp status Update the VLAN database. Cisco IOS Desktop Switching Software Configuration Guide 5-22 78-6511-04 . In the display. the VTP domain does not function properly if you do not assign the same password to each switch in the domain. make sure you configure at least one switch as the VTP server. The client switch receives VTP updates from a VTP server in the VTP domain and then modifies its configuration accordingly. Verify the VTP configuration.Chapter 5 Using the VLAN Trunk Protocol Creating and Maintaining VLANs CLI: Configuring VTP Client Mode When a switch is in VTP client mode. Beginning in privileged EXEC mode. The name can be from 1 to 32 characters. and return to privileged EXEC mode. If you do so. vlan database vtp client vtp domain domain-name Step 4 vtp password password-value (Optional) Set a password for the VTP domain. Configure the switch for VTP client mode.

Beginning in privileged EXEC mode. vlan database vtp transparent Step 3 Step 4 exit show vtp status Return to privileged EXEC mode. check the VTP Operating Mode field. When you enable VTP version 2 on a switch. The switch then does not send VTP updates and does not act on VTP updates received from other switches. Configure the switch for VTP transparent mode. CLI: Enabling VTP Version 2 VTP version 2 is disabled by default on VTP version 2-capable switches. However. a VTP transparent switch does forward received VTP advertisements on all of its trunk links. Cisco IOS Desktop Switching Software Configuration Guide 78-6511-04 5-23 . you disable VTP on the switch. The default setting is VTP server. CLI: Disabling VTP (VTP Transparent Mode) When you configure the switch for VTP transparent mode.Chapter 5 Creating and Maintaining VLANs Using the VLAN Trunk Protocol The “Finding More Information About IOS Commands” section on page 4-1 contains the path to the complete IOS documentation. In the display. The “Finding More Information About IOS Commands” section on page 4-1 contains the path to the complete IOS documentation. Verify the VTP configuration. This step disables VTP on the switch. follow these steps to configure the switch for VTP transparent mode: Command Step 1 Step 2 Purpose Enter VLAN database mode. every VTP version 2-capable switch in the VTP domain enables version 2.

propagate it throughout the administrative domain. VTP version 2 is disabled by default on VTP version 2-capable switches. Enable VTP version 2 on the switch. you must enable VTP version 2 for Token Ring VLAN switching to function properly. Note In a Token Ring environment. For more information on VTP version configuration guidelines. and return to privileged EXEC mode. check the VTP V2 Mode field. Every switch in the VTP domain must use the same VTP version. Step 1 Step 2 vlan database vtp v2-mode Step 3 exit Update the VLAN database. see the “VTP Version” section on page 5-18. follow these steps to enable VTP version 2: Command Purpose Enter VLAN configuration mode. In the display. Verify that VTP version 2 is enabled. Cisco IOS Desktop Switching Software Configuration Guide 5-24 78-6511-04 . Do not enable VTP version 2 unless every switch in the VTP domain supports version 2. Step 4 show vtp status The “Finding More Information About IOS Commands” section on page 4-1 contains the path to the complete IOS documentation.Chapter 5 Using the VLAN Trunk Protocol Creating and Maintaining VLANs Caution VTP version 1 and VTP version 2 are not interoperable on switches in the same VTP domain. Beginning in privileged EXEC mode.

and return to privileged EXEC mode. vlan database no vtp v2-mode exit Step 4 show vtp status The “Finding More Information About IOS Commands” section on page 4-1 contains the path to the complete IOS documentation. check the VTP V2 Mode field. follow these steps to disable VTP version 2: Command Step 1 Step 2 Step 3 Purpose Enter VLAN configuration mode. Disable VTP version 2. propagate it throughout the administrative domain. Update the VLAN database.Chapter 5 Creating and Maintaining VLANs Using the VLAN Trunk Protocol CLI: Disabling VTP Version 2 Beginning in privileged EXEC mode. Cisco IOS Desktop Switching Software Configuration Guide 78-6511-04 5-25 . Verify that VTP version 2 is disabled. In the display.

follow these steps to enable VTP pruning: Command Step 1 Step 2 Purpose Enter VLAN configuration mode. CLI: Monitoring VTP You monitor VTP by displaying its configuration information: the domain name. pruning is disabled. By default. Step 4 show vtp status Pruning is supported with VTP version 1 and version 2. see the “CLI: Changing the Pruning-Eligible List” section on page 5-45. The “Finding More Information About IOS Commands” section on page 4-1 contains the path to the complete IOS documentation. vlan database vtp pruning Step 3 exit Update the VLAN database. and return to privileged EXEC mode. You can also display statistics about the advertisements sent and received by the switch. You only need to enable pruning on one switch in VTP server mode. VLANs 2 through 1001 are pruning eligible on 2900 and 3500 XL trunk ports. In the display. check the VTP Pruning Mode field. the current VTP revision. You enable VTP pruning on a switch in VTP server mode. Beginning in privileged EXEC mode.Chapter 5 Using the VLAN Trunk Protocol Creating and Maintaining VLANs CLI: Enabling VTP Pruning Pruning increases available bandwidth by restricting flooded traffic to those trunk links that the traffic must use to access the destination devices. Enable pruning in the VTP administrative domain. Cisco IOS Desktop Switching Software Configuration Guide 5-26 78-6511-04 . Verify that your entries. propagate it throughout the administrative domain. Only VLANs included in the pruning-eligible list can be pruned. it is enabled for the entire VTP domain. By default. If you enable pruning on the VTP server. For information. and the number of VLANs.

or TrCRF. Token Ring-Net) VLAN state (active or suspended) Maximum transmission unit (MTU) for the VLAN Security Association Identifier (SAID) Bridge identification number for TrBRF VLANs Ring number for FDDI and TrCRF VLANs Parent VLAN number for TrCRF VLANs Spanning Tree Protocol (STP) type for TrCRF VLANs VLAN number to use when translating from one VLAN type to another The “Default VLAN Configuration” section on page 5-29 lists the default values and possible ranges for each VLAN media type. FDDI network entity title [NET]. Token Ring. Cisco IOS Desktop Switching Software Configuration Guide 78-6511-04 5-27 . follow these steps to monitor VTP activity: Command Step 1 Step 2 Purpose Display the VTP switch configuration information. TrBRF. Fiber Distributed Data Interface [FDDI].Chapter 5 Creating and Maintaining VLANs VLANs in the VTP Database Beginning in privileged EXEC mode. VLANs in the VTP Database You can set the following parameters when you add a new VLAN to or modify an existing VLAN in the VTP database: • • • • • • • • • • • VLAN ID VLAN name VLAN type (Ethernet. Display counters about VTP messages being sent and received. show vtp status show vtp counters The “Finding More Information About IOS Commands” section on page 4-1 contains the path to the complete IOS documentation.

FDDI-Net. see the “Configuring VTP” section on page 5-19. Switches running this IOS release do not support Token Ring or FDDI media. see the Catalyst 5000 Series Software Configuration Guide. Switches running this IOS release advertise information about the following Token Ring VLANs when running VTP version 2: • • Token Ring TrBRF VLANs Token Ring TrCRF VLANs For more information on configuring Token Ring VLANs. Before you can create a VLAN. The switch does not forward FDDI. the switch must be in VTP server mode or VTP transparent mode. VLAN Configuration Guidelines Follow these guidelines when creating and modifying VLANs in your network: • A maximum of 250 VLANs can be active on supported switches. For information on configuring VTP. and some models only support 64 VLANs. • • Cisco IOS Desktop Switching Software Configuration Guide 5-28 78-6511-04 . or TrBRF traffic. a remote device such as a Catalyst 5000 series switch with Token Ring connections could be managed from one of the supported switches. but it does propagate the VLAN configuration through VTP. 4 of the active VLANs (1002 to 1005) are reserved for Token Ring and FDDI. TrCRF.Chapter 5 VLANs in the VTP Database Creating and Maintaining VLANs Token Ring VLANs Although the 2900 and 3500 XL switches do not support Token Ring connections. If VTP reports that there are 254 active VLANs.

Table 5-6 Ethernet VLAN Defaults and Ranges Parameter VLAN ID VLAN name 802.10 SAID MTU size Translational bridge 1 Translational bridge 2 VLAN state Default 1 VLANxxxx. suspend Table 5-7 FDDI VLAN Defaults and Ranges Parameter VLAN ID VLAN name 802. you configure FDDI and Token Ring media-specific characteristics only for VTP global advertisements to other switches. where xxxx is the VLAN ID 100000+VLAN ID 1500 0 0 active Range 1–1005 No range 1–4294967294 1500–18190 0–1005 0–1005 active.Chapter 5 Creating and Maintaining VLANs VLANs in the VTP Database Default VLAN Configuration Table 5-6 through Table 5-10 shows the default configuration for the different VLAN media types. where xxxx is the VLAN ID 100000+VLAN ID 1500 None Range 1–1005 No range 1–4294967294 1500–18190 1–4095 Cisco IOS Desktop Switching Software Configuration Guide 78-6511-04 5-29 .10 SAID MTU size Ring number Default 1002 VLANxxxx. Because FDDI and Token Ring VLANs are not locally supported. Note Catalyst 2900 and 3500 XL switches support Ethernet interfaces exclusively.

where xxxx is the VLAN ID 100000+VLAN ID VTPv1 1500. VTPv2 4472 Cisco IOS Desktop Switching Software Configuration Guide Range 1–1005 No range 1–4294967294 1500–18190 5-30 78-6511-04 . suspend Table 5-9 Token Ring (TrBRF) VLAN Defaults and Ranges Parameter VLAN ID VLAN name 802. where xxxx is the VLAN ID 100000+VLAN ID 1500 0 ieee 0 0 active Range 1–1005 No range 1–4294967294 1500–18190 0–15 auto.10 SAID MTU size Bridge number STP type Translational bridge 1 Translational bridge 2 VLAN state Default 1004 VLANxxxx. ibm. ieee 0–1005 0–1005 active. suspend Table 5-8 FDDI-Net VLAN Defaults and Ranges Parameter VLAN ID VLAN name 802.10 SAID MTU size Default 1005 VLANxxxx.Chapter 5 VLANs in the VTP Database Creating and Maintaining VLANs Table 5-7 FDDI VLAN Defaults and Ranges (continued) Parameter Parent VLAN Translational bridge 1 Translational bridge 2 VLAN state Default 0 0 0 active Range 0–1005 0–1005 0–1005 active.

ieee 0–1005 0–1005 active. srt 0–13 0–13 disable. VTPv2 user-specified ibm 0 0 active Range 0–15 auto.10 SAID Ring Number Parent VLAN MTU size Translational bridge 1 Translational bridge 2 VLAN state Bridge mode ARE max hops STE max hops Backup CRF Default 1003 VLANxxxx. ibm. suspend srb. VTPv2 user-specified VTPv1 default 0. VTPv2 user-specified VTPv1 default 1500. suspend Table 5-10 Token Ring (TrCRF) VLAN Defaults and Ranges Parameter VLAN ID VLAN name 802. enable Cisco IOS Desktop Switching Software Configuration Guide 78-6511-04 5-31 . VTPv2 default 4472 0 0 active srb 7 7 disabled Range 1–1005 No range 1–4294967294 1–4095 0–1005 1500–18190 0–1005 0–1005 active.Chapter 5 Creating and Maintaining VLANs VLANs in the VTP Database Table 5-9 Token Ring (TrBRF) VLAN Defaults and Ranges (continued) Parameter Bridge number STP type Translational bridge 1 Translational bridge 2 VLAN state Default VTPv1 0. where xxxx is the VLAN ID 100000+VLAN ID VTPv1 default 0.

and you can display them by entering the privileged EXEC mode show vlan command. Figure 5-6 VTP Management: VLAN Configuration Tab Add a VLAN to the database. You cannot remove VLANs 1 or 1002-1005. The vlan. To display this window. change. Select an existing VLAN.Chapter 5 VLANs in the VTP Database Creating and Maintaining VLANs Configuring VLANs in the VTP Database You can use the VTP Management window (Figure 5-6) or the CLI to add. Cisco IOS Desktop Switching Software Configuration Guide 5-32 30767 78-6511-04 . and click Modify to change its parameters.dat.dat file is upgraded automatically. commands to add. and click the VLAN Configuration tab. In VTP server or transparent mode. The vlan. Click Help to for more information on using this window. You use the CLI vlan database command mode to add. VTP globally propagates these VLAN changes throughout the VTP domain. and delete VLANs are written to the file vlan. and click Remove to delete a VLAN from the database.dat file is stored in nonvolatile memory. Select a row. but you cannot return to an earlier version of Cisco IOS after you upgrade to this release. modify or remove VLAN configurations in the VTP database. change. and delete VLANs. select VLAN>VTP Management from the menu bar.

Note VLANs can be configured to support a number of parameters that are not discussed in detail in this section.Chapter 5 Creating and Maintaining VLANs VLANs in the VTP Database Caution You can cause inconsistency in the VLAN database if you attempt to manually delete the vlan. You use the interface configuration command mode to define the port membership mode and add and remove ports from VLAN. The results of these commands are written to the running-configuration file. refer to the Cisco IOS Desktop Switching Command Reference (online only). If you want to modify the VLAN configuration or VTP.dat file. use the VLAN database commands described in the Cisco IOS Desktop Switching Command Reference (online only). and you can display the file by entering the privileged EXEC mode show running-config command. For complete information on the commands and parameters that control VLAN configuration. Cisco IOS Desktop Switching Software Configuration Guide 78-6511-04 5-33 .

and return to privileged EXEC mode. If you do not specify the VLAN type. the VLAN is an Ethernet VLAN. To add a VLAN to the VLAN database. If no name is entered for the VLAN. For the list of default parameters that are assigned when you add a VLAN. 4-digit ID that can be a number from 1 to 1001. Beginning in privileged EXEC mode. Cisco IOS Desktop Switching Software Configuration Guide 5-34 78-6511-04 . exit Update the VLAN database. Step 3 Step 4 show vlan name vlan-name The “Finding More Information About IOS Commands” section on page 4-1 contains the path to the complete IOS documentation. see the “Default VLAN Configuration” section on page 5-29. propagate it throughout the administrative domain. assign a number and name to the VLAN. Verify the VLAN configuration. follow these steps to add an Ethernet VLAN: Command Step 1 Step 2 Purpose Enter VLAN database mode. the default is to append the vlan-id to the word VLAN. For example.Chapter 5 VLANs in the VTP Database Creating and Maintaining VLANs CLI: Adding an Ethernet VLAN Each VLAN has a unique. vlan database vlan vlan-id name vlan-name Add an Ethernet VLAN by assigning a number to it. VLAN0004 could be a default VLAN name.

Identify the VLAN. propagate it throughout the administrative domain. vlan database vlan vlan-id mtu mtu-size exit Step 4 show vlan vlan-id The “Finding More Information About IOS Commands” section on page 4-1 contains the path to the complete IOS documentation.Chapter 5 Creating and Maintaining VLANs VLANs in the VTP Database CLI: Modifying an Ethernet VLAN Beginning in privileged EXEC mode. and change the MTU size. Cisco IOS Desktop Switching Software Configuration Guide 78-6511-04 5-35 . Update the VLAN database. follow these steps to modify an Ethernet VLAN: Command Step 1 Step 2 Step 3 Purpose Enter VLAN configuration mode. and return to privileged EXEC mode. Verify the VLAN configuration.

any ports assigned to that VLAN become inactive. the VLAN is removed from all switches in the VTP domain.Chapter 5 VLANs in the VTP Database Creating and Maintaining VLANs CLI: Deleting a VLAN from the Database When you delete a VLAN from a switch that is in VTP server mode. propagate it throughout the administrative domain. Update the VLAN database. Remove the VLAN by using the VLAN ID. Caution When you delete a VLAN. You cannot delete the default VLANs for the different media types: Ethernet VLAN 1 and FDDI or Token Ring VLANs 1002 to 1005. Cisco IOS Desktop Switching Software Configuration Guide 5-36 78-6511-04 . Step 1 Step 2 Step 3 vlan database no vlan vlan-id exit Step 4 show vlan brief The “Finding More Information About IOS Commands” section on page 4-1 contains the path to the complete IOS documentation. follow these steps to delete a VLAN on the switch: Command Purpose Enter VLAN configuration mode. and return to privileged EXEC mode. When you delete a VLAN from a switch that is in VTP transparent mode. Verify the VLAN removal. They remain associated with the VLAN (and thus inactive) until you assign them to a new VLAN. Beginning in privileged EXEC mode. the VLAN is deleted only on that specific switch.

Enter interface configuration mode. In the display. first log in to the member switch by using the privileged EXEC rcommand command. configure terminal interface interface Step 3 Step 4 Step 5 Step 6 switchport mode access switchport access vlan 3 exit show interface interface-id switchport The “Finding More Information About IOS Commands” section on page 4-1 contains the path to the complete IOS documentation. which is the default management VLAN. and the Priority for Untagged Frames fields. Beginning in privileged EXEC mode. If you are assigning a port on a cluster member switch to a VLAN.Chapter 5 Creating and Maintaining VLANs VLANs in the VTP Database CLI: Assigning Static-Access Ports to a VLAN By default. Define the VLAN membership mode for this port. check the Operation Mode. Access Mode VLAN. Return to privileged EXEC mode. Verify the VLAN configuration. and define the interface to be added to the VLAN. For more information on how to use this command. Cisco IOS Desktop Switching Software Configuration Guide 78-6511-04 5-37 . refer to the Cisco IOS Desktop Switching Command Reference (online only). follow these steps to assign a port to a VLAN in the VTP database: Command Step 1 Step 2 Purpose Enter global configuration mode. Assign the port to the VLAN. all ports are static-access ports assigned to VLAN 1.

1Q to carry traffic for multiple VLANs over a single link. the default protocol. 100BaseT and Gigabit Ethernet trunks use Cisco Inter-Switch Link (ISL).Chapter 5 How VLAN Trunks Work Creating and Maintaining VLANs How VLAN Trunks Work A trunk is a point-to-point link that transmits and receives traffic between switches or between switches and routers. Figure 5-7 Catalyst 2900 Series XL and Catalyst 3500 Series XL Switches in an ISL Trunking Environment Catalyst 5000 series switch ISL trunk Catalyst 2900 XL switch ISL trunk ISL trunk ISL trunk Catalyst 3500 XL switch Catalyst 3500 XL switch VLAN3 Catalyst 2900 XL switch VLAN2 VLAN1 VLAN2 VLAN1 VLAN3 15929 Cisco IOS Desktop Switching Software Configuration Guide 5-38 78-6511-04 . Trunks carry the traffic of multiple VLANs and can extend VLANs across an entire network. or industry-standard IEEE 802. Figure 5-7 shows a network of switches that are connected by ISL trunks.

1Q trunk is the same on both ends of the trunk link.1Q Configuration Considerations IEEE 802. Secure ports Cisco IOS Desktop Switching Software Configuration Guide 78-6511-04 5-39 . spanning-tree loops might result. A static-access port can monitor the traffic of its VLAN on a trunk port. We recommend that you leave STP enabled on the native VLAN of an 802. • Trunks Interacting with Other Features ISL.1Q trunks impose some limitations on the trunking strategy for a network. and ATM trunking interacts with other switch features as described in Table 5-11.Chapter 5 Creating and Maintaining VLANs How VLAN Trunks Work IEEE 802. When configured as a network port.1Q trunks: • Make sure the native VLAN for an 802. If the native VLAN on one end of the trunk is different from the native VLAN on the other end. Disabling STP on the native VLAN of an 802. Make sure your network is loop-free before disabling STP. IEEE 802. A trunk port cannot be a secure port.1Q trunk or disable STP on every VLAN in the network.1Q trunk without disabling STP on every VLAN in the network can potentially cause STP loops. A network port receives all unknown unicast traffic on a VLAN. The following restrictions apply when using 802. Table 5-11 Trunks Interacting with Other Features Switch Feature Port monitoring Network port Trunk Port Interaction A trunk port cannot be a monitor port. a trunk port serves as the network port for all VLANs associated with the port.1Q.

unknown unicast packets cannot be blocked. However. all ports follow the parameters set for the first port to be added to the group. To display this window.Chapter 5 How VLAN Trunks Work Creating and Maintaining VLANs Table 5-11 Trunks Interacting with Other Features (continued) Switch Feature Trunk Port Interaction Blocking unicast The port block command can be used to block the and multicast forwarding of unknown unicast and multicast packets to packets on a trunk VLANs on a trunk. Port grouping ISL and 802. Then click the Assign VLANs tab or the Trunk Configuration tab. Configuring a Trunk Port You configure trunk ports by using the Assign VLANs (Figure 5-2) and Trunk Configuration (Figure 5-8) tabs of the VLAN Membership window. When a group is first created. all port cease to be trunks. select VLAN>VLAN Membership from the menu bar. if the trunk port is acting as a network port. the switch propagates the setting you entered to all ports in the group: • • • • • Allowed-VLAN list STP path cost for each VLAN STP port priority for each VLAN STP Port Fast setting Trunk status: if one port in a port group ceases to be a trunk. ATM ports are always trunk ports but cannot be part of an EtherChannel port group. Cisco IOS Desktop Switching Software Configuration Guide 5-40 78-6511-04 . If you change the configuration of one of the following parameters.1Q trunks can be grouped into EtherChannel port groups. but all trunks in the group must have the same configuration.

By default. Note Because trunk ports send and receive VTP advertisements. see the “Trunks Interacting with Other Features” section on page 5-39. You can modify this list. refer to the Cisco IOS Desktop Switching Command Reference (online only).1Q trunks only). first log in to the member switch by using the privileged EXEC rcommand command. the switch cannot receive any VTP advertisements. For information on trunk port interactions with other features. CLI: Configuring a Trunk Port You cannot have multi-VLAN and trunk ports configured on the same switch. You can remove VLANs from the allowed list to prevent traffic from those VLANs from passing over the trunk. Only VLANs included in the list can be pruned. VLANs 2-1001 are pruningeligible on trunk port. command. VLANs 1-1005 are allowed on each trunk. 29676 You can also configure a trunk port through the CLI on standalone. you must ensure that at least one trunk port is configured on the switch and that this trunk port is connected to the trunk port of a second switch.Chapter 5 Creating and Maintaining VLANs How VLAN Trunks Work Figure 5-8 VLAN Membership: Trunk Configuration Tab Select this tab to change the port membership mode to ISL trunk or 802.1Q trunk. Cisco IOS Desktop Switching Software Configuration Guide 78-6511-04 5-41 . and click Modify to change the allowed-VLAN list. the pruning-eligible list. If you are assigning a port on a cluster member switch to a VLAN. By default. For more information on how to use this command. Select a row or rows. and member switches. or the native VLAN for untagged traffic (802. Otherwise.

use the non-negotiate option on the DTP-capable device so that the switch port does not generate DTP frames. Cisco IOS Desktop Switching Software Configuration Guide 5-42 78-6511-04 .1Q encapsulation. Save the configuration. configure terminal interface interface_id switchport mode trunk switchport trunk encapsulation {isl | dot1q} Step 5 Step 6 end show interface interface-id switchport Return to privileged EXEC mode. check the Operational Mode and the Operational Trunking Encapsulation fields. Verify your entries. Configure the port to support ISL or 802. Enter the interface configuration mode and the port to be configured for trunking. If you are connecting a trunk port to a Catalyst 5000 switch or other DTP device. formerly known as Dynamic ISL (DISL).1Q trunk port: Command Step 1 Step 2 Step 3 Step 4 Purpose Enter global configuration mode.Chapter 5 How VLAN Trunks Work Creating and Maintaining VLANs Beginning in privileged EXEC mode. follow these steps to configure a port as an ISL or 802. Configure the port as a VLAN trunk. You must configure each end of the link with the same encapsulation type. In the display. Step 7 copy running-config startup-config Note This software release does not support trunk negotiation via the Dynamic Trunk Protocol (DTP). The “Finding More Information About IOS Commands” section on page 4-1 contains the path to the complete IOS documentation.

To restrict the traffic a trunk carries. Return to privileged EXEC. When VTP detects a newly enabled VLAN and the VLAN is in the allowed list for a trunk port. Beginning in privileged EXEC mode. the trunk port automatically becomes a member of the enabled VLAN. the trunk port does not become a member of the new VLAN. use the remove vlan-list parameter to remove specific VLANs from the allowed list. CLI: Defining the Allowed VLANs on a Trunk By default. When VTP detects a new VLAN and the VLAN is not in the allowed list for a trunk port. if VTP knows of the VLAN. Cisco IOS Desktop Switching Software Configuration Guide 78-6511-04 5-43 . A trunk port can become a member of a VLAN if the VLAN is enabled. In the display. configure terminal interface interface_id no switchport mode end show interface interface-id switchport The “Finding More Information About IOS Commands” section on page 4-1 contains the path to the complete IOS documentation. preventing traffic from those VLANs from passing over the trunk. All VLANs. are allowed on each trunk. 1 to 1005. Return the port to its default static-access mode. a trunk port sends to and receives traffic from all VLANs in the VLAN database. and if the VLAN is in the allowed list for the port. Enter the interface configuration mode and the port to be added to the VLAN. you can remove VLANs from the allowed list. Verify your entries.Chapter 5 Creating and Maintaining VLANs How VLAN Trunks Work CLI: Disabling a Trunk Port You can disable trunking on a port by returning it to its default static-access mode. check the Negotiation of Trunking field. However. follow these steps to disable trunking on a port: Command Step 1 Step 2 Step 3 Step 4 Step 5 Purpose Enter global configuration mode.

The “Finding More Information About IOS Commands” section on page 4-1 contains the path to the complete IOS documentation. Cisco IOS Desktop Switching Software Configuration Guide 5-44 78-6511-04 . Valid IDs are from 2 to 1001. Configure VLAN membership mode for trunks. configure terminal interface interface_id switchport mode trunk switchport trunk allowed vlan remove vlan-list Step 5 Step 6 Step 7 end Return to privileged EXEC.1Q trunk: Command Step 1 Step 2 Step 3 Step 4 Purpose Enter global configuration mode.Chapter 5 How VLAN Trunks Work Creating and Maintaining VLANs Beginning in privileged EXEC mode. show interface interface-id Verify your entries. use a hyphen to designate a range of IDs. follow these steps to modify the allowed list of a ISL or 802. The vlan-list parameter is a range of VLAN IDs Separate nonconsecutive VLAN IDs with a comma and no spaces. switchport allowed-vlan copy running-config startup-config Save the configuration. Enter interface configuration mode and the port to be added to the VLAN. Define the VLANs that are not allowed to transmit and receive on the port.

Beginning in privileged EXEC mode. Each trunk port has its own eligibility list. and select the trunk port for which VLANs should be pruned. VLANs that are pruning-ineligible receive flooded traffic. The “Finding More Information About IOS Commands” section on page 4-1 contains the path to the complete IOS documentation. Enter interface configuration mode. follow these steps to remove VLANs from the pruning-eligible list on a trunk port: Command Step 1 Step 2 Purpose Enter global configuration mode. Verify your settings. Valid IDs are from 2 to 1001.Chapter 5 Creating and Maintaining VLANs How VLAN Trunks Work CLI: Changing the Pruning-Eligible List The pruning-eligible list applies only to trunk ports. configure terminal interface interface-id Step 3 switchport trunk pruning vlan remove vlan-id Step 4 Step 5 exit show interface interface-id switchport Return to privileged EXEC mode. Cisco IOS Desktop Switching Software Configuration Guide 78-6511-04 5-45 . The “CLI: Enabling VTP Pruning” section on page 5-26 describes how to enable VTP pruning. Enter the VLANs to be removed from the pruning-eligible list. use a hyphen to designate a range of IDs. Separate nonconsecutive VLAN IDs with a comma and no spaces. VTP Pruning must be enabled for the following procedure to take effect.

For information about 802.1Q trunk. By default.1Q trunk: Command Purpose Enter global configuration mode. the switch forwards untagged traffic with the native VLAN configured for the port. The “Finding More Information About IOS Commands” section on page 4-1 contains the path to the complete IOS documentation. the switch transmits the packet with a tag. otherwise. Cisco IOS Desktop Switching Software Configuration Guide 5-46 78-6511-04 . follow these steps to configure the native VLAN on an 802. Verify your settings. Enter interface configuration mode. Note The native VLAN can be assigned any VLAN ID. Valid IDs are from 1 to 1001.1Q configuration issues.Chapter 5 How VLAN Trunks Work Creating and Maintaining VLANs CLI: Configuring the Native VLAN for Untagged Traffic A trunk port configured with 802. Configure the VLAN that is sending and receiving untagged traffic on the trunk port. The native VLAN is VLAN 1 by default. and define the interface that is configured as the 802. see the “IEEE 802. Beginning in privileged EXEC mode. and it is not dependent on the management VLAN.1Q tagging can receive both tagged and untagged traffic. Step 1 Step 2 configure terminal interface interface-id Step 3 switchport trunk native vlan vlan-id show interface interface-id switchport Step 4 If a packet has a VLAN ID the same as the outgoing port native VLAN ID.1Q Configuration Considerations” section on page 5-39. the packet is transmitted untagged.

it is assigned the value of the port as its port default priority. Cisco IOS Desktop Switching Software Configuration Guide 78-6511-04 5-47 . The tag is examined and understood by each device before any broadcasts or transmissions to other switches. the tag is removed before the frame is transmitted to the target end station. QoS uses classification and scheduling to transmit network traffic from the switch in a predictable manner. or end stations.1p Class of Service The 2900 XL and 3500 XL switches provide QoS-based IEEE 802. QoS classifies frames by assigning priority-indexed CoS values to them and gives preference to higher-priority traffic such as telephone calls. You assign this value by using the CLI or CMS software. VLANs that are assigned on trunk or access ports without identification or a tag are called native or untagged frames. a unique identifier (the tag) is inserted in each frame header before it is forwarded. Port Scheduling Each port on the switch has a single receive queue buffer (the ingress port) for incoming traffic. routers. refer to the Catalyst 6000 documentation. Based on rules you define. How Class of Service Works Before you set up 802.Chapter 5 Creating and Maintaining VLANs How VLAN Trunks Work Configuring 802. For ISL or IEEE 802. Port Priority Frames received from users in the administratively-defined VLANs are classified or tagged for transmission to other devices.1Q frames with tag information. and they should be understood to ensure compatibility. There are differences in the 802. A tagged frame continues to use its assigned CoS value when it passes through the ingress port. the default priority of the input port is used. When an untagged frame arrives. the priority value from the header frame is used.1p class of service (CoS) values.1p implementation.1p CoS on a 2900 or 3500 XL switch that operates with the Catalyst 6000 family of switches. For native frames. When the frame reaches the last switch or router.

Cisco IOS Desktop Switching Software Configuration Guide 5-48 78-6511-04 . Catalyst 2900 XL switches with 4 MB of DRAM and the WS-X2914-XL and the WS-X2922-XL modules only have one transmit queue and do not support QoS. Frames with a priority value of 4 through 7 are sent to a high-priority queue. depending on the frame tag or the port information. Table 5-12 Transmit Queue Information Transmit queue category1 Transmit Queues 2900 XL switches.1p user priority) Frames with a priority value of 0 through 3 are sent to a normal-priority queue. 1. Frames with a priority value of 0 through 3 are sent to a normal-priority queue. Frames with a priority value of 4 through 7 are sent to a high-priority queue. Frames in the normal-priority queue are forwarded only after frames in the high-priority queue are forwarded.Chapter 5 How VLAN Trunks Work Creating and Maintaining VLANs CoS configures each transmit port (the egress port) with a normal-priority transmit queue and a high-priority transmit queue. Gigabit Ethernet modules (802.1p user priority) 3500 XL switches. Table 5-12 shows the two categories of switch transmit queues. 2900 XL Ethernet modules (802.

For load sharing using STP port priorities. Verify your entries. you divide the traffic between the links according to which VLAN the traffic belongs. In the display. each load-sharing link can be connected to the same switch or to two different switches. For load sharing using STP path costs. both load-sharing links must be connected to the same switch. Load Sharing Using STP Load sharing divides the bandwidth supplied by parallel trunks connecting switches. If you assign a priority level from 4 to 7. You configure load sharing on trunk ports by using STP port priorities or STP path costs. Enter the interface to be configured. check the Priority for Untagged Frames field. STP normally blocks all but one parallel link between switches. Set the port priority on the interface. Cisco IOS Desktop Switching Software Configuration Guide 78-6511-04 5-49 . frames are forwarded to the normal priority queue of the output port. If you assign a priority level from 0 to 3. To avoid loops. follow these steps to set the port priority for untagged (native) Ethernet frames: Command Step 1 Step 2 Step 3 Purpose configure terminal interface interface switchport priority default default-priority-id Enter global configuration mode. With load sharing. frames are forwarded to the high-priority queue of the output port. The “Finding More Information About IOS Commands” section on page 4-1 contains the path to the complete IOS documentation.Chapter 5 Creating and Maintaining VLANs How VLAN Trunks Work CLI: Configuring the CoS Port Priorities Beginning in privileged EXEC mode. Step 4 Step 5 end show interface interface-id switchport Return to privileged EXEC mode.

trunk 1 carries traffic for VLANs 8 through 10. VLANs 8 through 10 retain the default port priority of 128 on trunk 2. In this example. VLANs 3 through 6 retain the default port priority of 128 on trunk 1. To display this window. the trunk with the lower priority takes over and carries the traffic for all of the VLANs. or consult the online help in the application. Cisco IOS Desktop Switching Software Configuration Guide 5-50 78-6511-04 . For more information about the STP window. see the “Configuring the Spanning Tree Protocol” section on page 4-62. One trunk port transmits or receives all traffic for the VLAN. Load Sharing Using STP Port Priorities When two ports on the same switch form a loop. No duplication of traffic occurs over any trunk port. Figure 5-9 shows two trunks connecting supported switches. In this way. VLANs 3 through 6 are assigned a port priority of 10 on trunk 2. You can set the priorities on a parallel trunk port so that the port carries all the traffic for a given VLAN. The trunk port with the higher priority (lower values) for a VLAN is forwarding traffic for that VLAN.Chapter 5 How VLAN Trunks Work Creating and Maintaining VLANs You can change STP port parameters by using the Port Parameters tab of the Spanning Tree Protocol window or by using the CLI. the switches are configured as follows: • • • • VLANs 8 through 10 are assigned a port priority of 10 on trunk 1. The trunk port with the lower priority (higher values) for the same VLAN remains in a blocking state for that VLAN. and trunk 2 carries traffic for VLANs 3 through 6. Then click the Port Parameters tab. If the active trunk fails. the STP port priority setting determines which port is enabled and which port is in standby mode. select Device>Spanning-Tree Protocol from the menu bar.

Chapter 5 Creating and Maintaining VLANs How VLAN Trunks Work Figure 5-9 Load Sharing by Using STP Port Priorities Switch 1 Trunk 1 VLANs 8-10 (priority 10) VLANs 3-6 (priority 128) Trunk 2 VLANs 3-6 (priority 10) VLANs 8-10 (priority 128) 15932 Switch 2 CLI: Configuring STP Port Priorities and Load Sharing Beginning in privileged EXEC mode. and define Fa0/1 as the interface to be configured as a trunk. Enter global configuration mode. check the VTP Operating Mode and the VTP Domain Name fields. In the display. Verify the VTP configuration on both Switch 1 and Switch 2. Enter interface configuration mode. follow these steps to configure the network shown in Figure 5-9: Command Step 1 Step 2 Purpose On Switch 1. Step 6 Step 7 Step 8 show vlan configure terminal interface fa0/1 Verify that the VLANs exist in the database on Switch 1. Cisco IOS Desktop Switching Software Configuration Guide 78-6511-04 5-51 . enter VLAN configuration mode. Return to privileged EXEC mode. Configure a VTP administrative domain. The domain name can be from 1 to 32 characters. vlan database vtp domain domain-name Step 3 Step 4 Step 5 vtp server exit show vtp status Configure Switch 1 as the VTP server.

Verify the VLAN configuration. The trunk defaults to ISL trunking. and 10. Return to privileged EXEC mode. Repeat Steps 7 through 11 on Switch 2 to configure the trunk ports on interface Fa0/1 and Fa0/2. 5. and define the interface to set the STP port priority.Chapter 5 How VLAN Trunks Work Creating and Maintaining VLANs Command Step 9 Purpose Configure the port as a trunk port. Assign the port priority of 10 for VLANs 8. Return to privilege EXEC mode. Enter interface configuration mode. Verify the Switch 2 has learned the VLAN configuration. and 6. Enter interface configuration mode. Enter global configuration mode on Switch 1. Cisco IOS Desktop Switching Software Configuration Guide 5-52 78-6511-04 . switchport mode trunk end show interface fa0/1 switchport Step 10 Step 11 Step 12 Step 13 Step 14 show vlan When the trunk links come up. Step 15 Step 16 configure terminal interface fa0/1 Step 17 Step 18 Step 19 spanning-tree vlan 8 9 10 port-priority 10 end interface fa0/2 Step 20 Step 21 Step 22 spanning-tree vlan 3 4 5 6 port priority 10 exit show running-config The “Finding More Information About IOS Commands” section on page 4-1 contains the path to the complete IOS documentation. Assign the port priority of 10 for VLANs 3. Verify your entries. and define the interface to set the STP port priority. 9. VTP passes the VTP and VLAN information to Switch 2. 4. Repeat Steps 7 through 11 on Switch 1 for interface Fa0/2. Return to global configuration mode.

In Figure 5-10. VLANs 8 through 10 retain the default 100BaseT path cost on trunk port 1 of 19. and redundancy is maintained in the event of a lost link. trunk ports 1 and 2 are 100BaseT ports. Figure 5-10 Load-Sharing Trunks with Traffic Distributed by Path Cost Switch 1 Trunk port 1 VLANs 2-4 (path cost 30) VLANs 8-10 (path cost 19) Trunk port 2 VLANs 8-10 (path cost 30) VLANs 2-4 (path cost 19) 16591 Switch 2 Cisco IOS Desktop Switching Software Configuration Guide 78-6511-04 5-53 .Chapter 5 Creating and Maintaining VLANs How VLAN Trunks Work Load Sharing Using STP Path Cost You can configure parallel trunks to share VLAN traffic by setting different path costs on a trunk and associating the path costs with different sets of VLANs. VLANs 8 through 10 are assigned a path cost of 30 on trunk port 2. VLANs 2 through 4 retain the default 100BaseT path cost on trunk port 2 of 19. The VLANs keep the traffic separate. The path costs for the VLANs are assigned as follows: • • • • VLANs 2 through 4 are assigned a path cost of 30 on trunk port 1. because no loops exist. STP does not disable the ports.

Enter interface configuration mode.Chapter 5 How VLAN Trunks Work Creating and Maintaining VLANs CLI: Configuring STP Path Costs and Load Sharing Beginning in privileged EXEC mode. and set the spanning-tree path cost to 30 for VLANs 8. The trunk defaults to ISL trunking. and define Fa0/1 as the interface to be configured as a trunk. make sure that interface Fa0/1 and Fa0/2 are configured as trunk ports. Switch 1 receives the VTP information from the other switches. follow these steps to configure the network shown in Figure 5-10: Command Step 1 Step 2 Purpose Enter global configuration mode on Switch 1. 9. Verify that Switch 1 has learned the VLAN configuration. In the display. 3. configure terminal interface fa0/1 Step 3 switchport mode trunk end Step 4 Step 5 Step 6 show running-config Verify your entries. Step 7 show vlan When the trunk links come up. and 4. Configure the port as a trunk port. Return to global configuration mode. and 10. Repeat Steps 2 through 4 on Switch 1 interface Fa0/2. Enter interface configuration mode. Step 8 Step 9 configure terminal interface fa0/1 Step 10 Step 11 Step 12 spanning-tree vlan 2 3 4 cost 30 end Cisco IOS Desktop Switching Software Configuration Guide 5-54 78-6511-04 . and define Fa0/1 as the interface to set the STP cost. Repeat Steps 9 through 11 on Switch 1 interface Fa0/2. Return to global configuration mode. Enter global configuration mode. Set the spanning-tree path cost to 30 for VLANs 2.

The switch continues to monitor the packets directed to the port and sends a query to the VMPS when it Cisco IOS Desktop Switching Software Configuration Guide 78-6511-04 5-55 . it searches its database for a MAC address-to-VLAN mapping. and the VMPS is in secure mode. verify that the path costs are set correctly for interface Fa0/1 and Fa0/2. Secure mode determines whether the server shuts down the port when a VLAN is not allowed on it or just denies the port access to the VLAN. the VMPS sends an access-denied or a port-shutdown response. When the VMPS receives a VQP request from a client switch.Chapter 5 Creating and Maintaining VLANs How the VMPS Works Command Step 13 Step 14 Purpose Return to privileged EXEC mode. exit show running-config The “Finding More Information About IOS Commands” section on page 4-1 contains the path to the complete IOS documentation. If the switch receives an access-denied response from the VMPS. the VMPS verifies the requesting port against this group and responds as follows: – If the VLAN is allowed on the port. and the VMPS is not in secure mode. the VMPS sends an access-denied response. the VMPS sends the VLAN name to the client in response. – If the VLAN is not allowed on the port. depending on the secure mode of the VMPS. In response to a request. the VMPS takes one of the following actions: • If the assigned VLAN is restricted to a group of ports. How the VMPS Works A switch running this software release acts as a client to the VLAN Membership Policy Server (VMPS) and communicates with it through the VLAN Query Protocol (VQP). the VMPS sends a port-shutdown response. it continues to block traffic from the MAC address to or from the port. • If the VLAN in the database does not match the current VLAN on the port and active hosts exist on the port. The server response is based on this mapping and whether or not the server is in secure mode. In the display. Verify your entries. – If the VLAN is not allowed on the port.

see the “How the VMPS Works” section on page 5-55. it uses the domain name from the first VTP packet it receives on its trunk port from the VMPS. Multiple hosts (MAC addresses) can be active on a dynamic port if they are all in the same VLAN. it disables the port. the switch does not forward traffic to or from this port until the VMPS provides the VLAN assignment. If the link goes down on a dynamic port. Any hosts that come online through the port are checked again with the VMPS before the port is assigned to a VLAN. the VMPS sends an access-denied or port-shutdown response. If the client switch was not previously configured. Cluster Management software. however. Dynamic Port VLAN Membership A dynamic (nontrunking) port on the switch can belong to only one VLAN. You can also use an explicit entry in the configuration table to deny access to specific MAC addresses for security reasons. When the link comes up. the VMPS shuts down a dynamic port if more than 20 hosts are active on the port. the VMPS either denies the request or shuts down the port (depending on the VMPS secure mode setting). If there is a match. For more information on possible VMPS responses. it includes its domain name in the query packet to the VMPS to obtain its VLAN number. If the switch receives a port-shutdown response from the VMPS. The VMPS verifies that the domain name in the packet matches its own domain name before accepting the request and responds to the client with the assigned VLAN number for the client. If there is no match. The VMPS receives the source MAC address from the first packet of a new host connected to the dynamic port and attempts to match the MAC address to a VLAN in the VMPS database. Cisco IOS Desktop Switching Software Configuration Guide 5-56 78-6511-04 . If the client switch was previously configured. the VMPS sends the VLAN number for that port. or SNMP. If you enter the none keyword for the VLAN name. the port returns to an isolated state and does not belong to a VLAN.Chapter 5 How the VMPS Works Creating and Maintaining VLANs identifies a new address. The port must be manually reenabled by using the CLI.

the command switch adds the name of the switch before the Fa. If the VMPS is in secure mode. For example. Use a Catalyst 5000 series switch as the VMPS. and the MAC address-to-VLAN mapping. such as the domain name. the VMPS sends the fallback VLAN name to the client. If the switch is a cluster member. Cisco IOS Desktop Switching Software Configuration Guide 78-6511-04 5-57 . the VMPS sends an access-denied response. it sends a port-shutdown response. The VMPS database configuration file on the server must use the 2900 XL and 3500 XL convention for naming ports. the fall-back VLAN name. These naming conventions must be used in the VMPS database configuration file when it is configured to support a cluster. For example. If you connect a device with a MAC address that is not in the database. If you do not configure a fallback VLAN and the MAC address does not exist in the database. The file contains VMPS information.Chapter 5 Creating and Maintaining VLANs How the VMPS Works VMPS Database Configuration File The VMPS contains a database configuration file that you create. This ASCII text file is stored on a switch-accessible TFTP server that functions as a VMPS server. es3%Fa02 refers to fixed 10/100 port 2 on member switch 3. A 2900 or 3500 XL switch running this software release cannot act as the VMPS. You can configure a fallback VLAN name. Fa0/5 is fixed-port number 5.

9abc vlan-name ExecStaff address fedc.2. vmps domain WBU vmps mode open vmps fallback default vmps no-domain-req deny ! ! !MAC Addresses ! vmps-mac-addrs ! ! address <addr> vlan-name <vlan_name> ! address 0012.168.5678.a080 vlan-name hardware address aabb.1 port Fa1/3 device 172.6509.2 port es5%Fa0/2 device 192.ba98.2.eeff vlan-name Green address 1223.1245 vlan-name Purple ! !Port Groups ! !vmps-port-group <group-name> ! device <device-id> { port <port-name> | all-ports } ! vmps-port-group WiringCloset1 device 192.16.168.168.Chapter 5 How the VMPS Works Creating and Maintaining VLANs The following example shows a sample VMPS database configuration file as it appears on a Catalyst 5000 series switch.2233.7654 vlan-name --NONE-address fedc.ba23.4455 vlan-name hardware address 0000.1. !vmps mode { open | secure } ! The default mode is open.1 port Fa1/4 vmps-port-group “Executive Row” device 192.1. !vmps domain <domain-name> ! The VMPS domain must be defined.2. !vmps fallback <vlan-name> !vmps no-domain-req { allow | deny } ! ! The default value is allow.3 all-ports ! !VLAN groups ! !vmps-vlan-group <group-name> ! vlan-name <vlan-name> Cisco IOS Desktop Switching Software Configuration Guide 5-58 78-6511-04 .168.ccdd.2 port es5%Fa0/1 device 192.

Secure ports cannot be dynamic ports. the spanning-tree Port Fast feature is automatically enabled for that port. You can disable Port Fast mode on a dynamic port. When you configure a port as dynamic. The Port Fast mode accelerates the process of bringing the port into the forwarding state. In this case.1 port Fa0/9 vmps-port-policies vlan-name Purple device 192.Chapter 5 Creating and Maintaining VLANs How the VMPS Works ! vmps-vlan-group Engineering vlan-name hardware vlan-name software ! !VLAN port Policies ! !vmps-port-policies {vlan-name <vlan_name> | vlan-group <group-name> } ! { port-group <group-name> | device <device-id> port <port-name> } ! vmps-port-policies vlan-group Engineering port-group WiringCloset1 vmps-port-policies vlan-name Green device 192. the switch retains the setting and applies it if the port is later configured as an access port.1.168. Trunk ports cannot be dynamic ports. but it is possible to enter the switchport access vlan dynamic command for a trunk port. • • • Cisco IOS Desktop Switching Software Configuration Guide 78-6511-04 5-59 . For the cluster-based port-naming conventions. The communication between a cluster of switches and VMPS is managed by the command switch and includes port-naming conventions that are different from standard port names.2. You must turn off trunking on the port before the dynamic access setting takes effect.168.2 port Fa0/10 port-group “Executive Row” VMPS Configuration Guidelines The following guidelines and restrictions apply to dynamic port VLAN membership: • • You must configure the VMPS before you configure ports as dynamic. see the “VMPS Database Configuration File” section on page 5-57. You must disable port security on the port before it becomes dynamic.

To display this window.Chapter 5 How the VMPS Works Creating and Maintaining VLANs • • Dynamic ports cannot be network ports or monitor ports. Table 5-13 Default VMPS Client and Dynamic Port Configuration Feature VMPS domain server VMPS reconfirm interval VMPS server retry count Dynamic ports Default Configuration None 60 minutes 3 None configured Configuring Dynamic VLAN Membership You configure dynamic VLANs by using the VMPS Server (Figure 5-11) and the VMPS Info (Figure 5-12) tabs of the VMPS Configuration window. select Cluster>VMPS Configuration from the menu bar. The VTP management domain of the VMPS client and the VMPS server must be the same. and click the VMPS Server or the VMPS Info tab. Cisco IOS Desktop Switching Software Configuration Guide 5-60 78-6511-04 . Default VMPS Configuration Table 5-13 shows the default VMPS and dynamic port configuration on client switches.

For more information on how to use this command. You can also configure VMPS through the CLI on standalone. and click Add. and click Make Primary to make the address the primary one. refer to the Cisco IOS Desktop Switching Command Reference (online only).Chapter 5 Creating and Maintaining VLANs How the VMPS Works Figure 5-11 VMPS Configuration: VMPS Server Tab Enter the IP address of the VMPS server to be queried by the client. command. first log in to the member switch by using the privileged EXEC rcommand command. Only one address can be primary. and member switches. Highlight the address. select VLAN>VLAN Membership from the menu bar. You also need to access the VLAN Membership window to assign the port connected to the end station for dynamic VLAN membership and the port connected to the VMPS server for trunking. the client queries these addresses if no response is received from the primary server. To display this window. Cisco IOS Desktop Switching Software Configuration Guide 78-6511-04 30814 5-61 . If you are configuring VMPS on a cluster member switch to a VLAN. You can enter up to three secondary addresses.

Chapter 5 How the VMPS Works Creating and Maintaining VLANs Figure 5-12 VMPS Configuration: VMPS Info Tab Number of times the client tries to reach the current server before switching to an alternate. Cisco IOS Desktop Switching Software Configuration Guide 5-62 30815 78-6511-04 . Number of minutes between reconfirmation of VLAN assignments. Click to reconfirm dynamic VLAN membership. Status is updated in the Reconfirmation Status section. Default is 3. Default is 60.

Verify the VMPS server entry. In the display. You can enter up to three secondary server addresses. The “Finding More Information About IOS Commands” section on page 4-1 contains the path to the complete IOS documentation. follow these steps to enter the IP address of the VMPS: Command Step 1 Step 2 Step 3 Purpose Enter global configuration mode. If the VMPS is being defined for a cluster of switches. Enter the IP address for the switch acting as a secondary VMPS server. enter the address on the command switch. Cisco IOS Desktop Switching Software Configuration Guide 78-6511-04 5-63 . check the VMPS Domain Server field. Beginning in privileged EXEC mode.Chapter 5 Creating and Maintaining VLANs How the VMPS Works CLI: Entering the IP Address of the VMPS You must enter the IP address of the Catalyst 5000 switch or the other device acting as the VMPS to configure the 2900 or 3500 XL switch as a client. configure terminal vmps server ipaddress primary vmps server ipaddress Step 4 Step 5 end show vmps Return to privileged EXEC mode. Enter the IP address of the switch acting as the primary VMPS server.

For more information. first log into the member switch by using the privileged EXEC rcommand command. Verify the entry. Caution Dynamic port VLAN membership is for end stations. refer to the Cisco IOS Desktop Switching Command Reference (online only). check the Operational Mode field. The switch port that is connected to the VMPS server should be configured as a trunk. The dynamic-access port must be connected to an end station. In the display. Enter interface configuration mode and the switch port that is connected to the end station. see the “CLI: Configuring a Trunk Port” section on page 5-41. Beginning in privileged EXEC mode. Cisco IOS Desktop Switching Software Configuration Guide 5-64 78-6511-04 . The “Finding More Information About IOS Commands” section on page 4-1 contains the path to the complete IOS documentation. Configure the port as eligible for dynamic VLAN membership. Step 1 Step 2 configure terminal interface interface Step 3 Step 4 switchport mode access switchport access vlan dynamic Step 5 Step 6 end show interface interface switchport Return to privileged EXEC mode. follow these steps to configure a dynamic port on the VMPS client switches: Command Purpose Enter global configuration mode. For more information on how to use this command. Connecting dynamic ports to other switches can cause a loss of connectivity.Chapter 5 How the VMPS Works Creating and Maintaining VLANs CLI: Configuring Dynamic Ports on VMPS Clients If you are configuring a port on a member switch as a dynamic port. Set the port to access mode.

vmps reconfirm show vmps The “Finding More Information About IOS Commands” section on page 4-1 contains the path to the complete IOS documentation. Cisco IOS Desktop Switching Software Configuration Guide 78-6511-04 5-65 .Chapter 5 Creating and Maintaining VLANs How the VMPS Works CLI: Reconfirming VLAN Memberships Beginning in privileged EXEC mode. Verify the dynamic VLAN reconfirmation status. follow these steps to confirm the dynamic port VLAN membership assignments that the switch has received from the VMPS: Command Step 1 Step 2 Purpose Reconfirm dynamic port VLAN membership.

Beginning in privileged EXEC mode. The default is 60 minutes.Chapter 5 How the VMPS Works Creating and Maintaining VLANs CLI: Changing the Reconfirmation Interval VMPS clients periodically reconfirm the VLAN membership information received from the VMPS. In the display. Verify the dynamic VLAN reconfirmation status. check the Reconfirm Interval field. this parameter must be equal to or greater than the reconfirmation setting on the command switch. You can set the number of minutes after which reconfirmation occurs. In addition. The “Finding More Information About IOS Commands” section on page 4-1 contains the path to the complete IOS documentation. Enter a number from 1 to 120. refer to the Cisco IOS Desktop Switching Command Reference (online only). Cisco IOS Desktop Switching Software Configuration Guide 5-66 78-6511-04 . For more information about this command. Enter the number of minutes between reconfirmations of the dynamic VLAN membership. configure terminal vmps reconfirm minutes Step 3 Step 4 end show vmps Return to privileged EXEC mode. you must first log into the member switch by using the privileged EXEC rcommand command. If you are configuring a member switch in a cluster. follow these steps to change the reconfirmation interval: Command Step 1 Step 2 Purpose Enter global configuration mode.

Change the retry count. If no response is received after this many tries. check the Server Retry Count field. follow these steps to change the number of times that the switch attempts to contact the VMPS before querying the next server: Command Step 1 Step 2 Purpose Enter global configuration mode. Reconfirm Interval Server Retry Count Cisco IOS Desktop Switching Software Configuration Guide 78-6511-04 5-67 . The number of times VQP resends a query to the VMPS.Chapter 5 Creating and Maintaining VLANs How the VMPS Works CLI: Changing the Retry Count Beginning in privileged EXEC mode. The number of minutes the switch waits before reconfirming the VLAN-to-MAC-address assignments. The “Finding More Information About IOS Commands” section on page 4-1 contains the path to the complete IOS documentation. configure terminal vmps retry count Step 3 Step 4 exit show vmps Return to privileged EXEC mode. In the display. The switch queries the VMPS using version 1 of VQP. The switch displays the following information about the VMPS: VMPS VQP Version The version of VQP used to communicate with the VMPS. Verify your entry. Administering and Monitoring the VMPS You can display information about the VMPS by using the privileged EXEC show vmps command. the switch starts to query the secondary VMPS. the default is 3. The retry range is from 1 to 10.

This can happen automatically when the reconfirmation interval expired. Troubleshooting Dynamic Port VLAN Membership The VMPS shuts down a dynamic port under these conditions: • The VMPS is in secure mode. enter the interface configuration mode no shutdown command. Cisco IOS Desktop Switching Software Configuration Guide 5-68 78-6511-04 . or you can force it by entering the privileged EXEC vmps reconfirm command or its Cluster Management software or SNMP equivalent. More than 20 active hosts reside on a dynamic port. The VMPS shuts down the port to prevent the host from connecting to the network. • To reenable a shut-down dynamic port.Chapter 5 How the VMPS Works Creating and Maintaining VLANs VMPS domain server The IP address of the configured VLAN membership policy servers. The switch currently sends queries to the one marked current. VMPS Action The result of the most recent reconfirmation attempt. and it will not allow the host to connect to the port. The one marked primary is the primary server.

7. In this example. these assumptions apply: • • • • The VMPS server and the VMPS client are separate switches. The Catalyst 5000 series Switch 1 is the primary VMPS server.20.Chapter 5 Creating and Maintaining VLANs How the VMPS Works Dynamic Port VLAN Membership Configuration Example Figure 5-13 shows a network with a VMPS server switch and VMPS client switches with dynamic ports. Cisco IOS Desktop Switching Software Configuration Guide 78-6511-04 5-69 .db and is stored on the TFTP server with the IP address 172.22. The Catalyst 5000 series Switch 3 and Switch 10 are secondary VMPS servers. End stations are connected to these clients: – Catalyst 2900 XL Switch 2 – Catalyst 3500 XL Switch 9 • The database configuration file is called Bldg-G.

20.157 Client End station 2 Dynamic-access port Switch 9 172.20.20.26.158 Trunk port 30769 Secondary VMPS Server 3 Switch 10 172.152 Switch 4 172.20.20.20.155 Switch 7 172.26.154 Switch 6 172.151 Trunk port 172.153 Ethernet segment (Trunk link) Switch 5 172.26.26.Chapter 5 How the VMPS Works Creating and Maintaining VLANs Figure 5-13 Dynamic Port VLAN Membership Configuration Catalyst 5000 series Primary VMPS Server 1 Switch 1 End station 1 Dynamic-access port Switch 2 TFTP server Router 172.20.20.26.22.150 Client 172.26.20.159 Cisco IOS Desktop Switching Software Configuration Guide 5-70 78-6511-04 .7 Secondary VMPS Server 2 Switch 3 172.20.26.26.26.20.26.156 Switch 8 172.