Configuring the VTP Version
Two versions of VTP are available for use in a management domain. Catalyst switches are capable of running either VTP version 1 or VTP version 2. Within a management domain, the two versions are not interoperable. Therefore, the same VTP version must be configured on each switch in a domain. VTP version 1 is the default protocol on a switch.
If a switch is capable of running VTP version 2, however, a switch may coexist with other version 1 switches, as long as its VTP version 2 is not enabled. This situation becomes important if you want to use version 2 in a domain. Then, only one server mode switch needs to have VTP version 2 enabled. The new version number is propagated to all other version 2-capable switches in the domain, causing them all to automatically enable version 2 for use.
By default, VTP version 1 is enabled. Version 2 can be enabled or disabled using the v2 option.
The two versions of VTP differ in the features they support. VTP version 2 offers the following additional features over version 1:
• Version-dependent transparent mode—VTP version 1 in transparent mode matches the VTP version and domain name before forwarding the information to other switches using VTP. VTP version 2 in transparent mode differs by forwarding the VTP messages without checking the version number. Because only one domain is supported in a switch, the domain name doesn't have to be checked.
• Consistency checks—VTP version 2 performs consistency checks on the VTP and VLAN parameters entered from the CLI or by Simple Network Management Protocol (SNMP). This checking helps prevent errors in such things as VLAN names and numbers from being propagated to other switches in the domain. However, no consistency checks are performed on VTP messages that are received on trunk links or on configuration and database data that is read from NVRAM.
• Token Ring support—VTP version 2 supports the use of Token Ring switching and Token Ring VLANs. (If Token Ring switching is being used, VTP version 2 must be enabled.) The section "Token Ring VLANs" later in this chapter discusses these topics in detail.
• Unrecognized Type-Length-Value (TLV) support—VTP version 2 switches will propagate received configuration change messages out other trunk links, even if the switch supervisor is not able to parse or understand the message. For example, a VTP advertisement contains a Type field to denote what type of VTP message is being sent. VTP message type 1 is a summary advertisement, and message type 2 is a subset advertisement. An extension to VTP could be in use that utilizes other message types and other message length values. Instead of dropping the unrecognized VTP message, version 2 will still propagate the information and keep a copy in NVRAM.
Configuring the VTP Version on an IOS-Based Switch
On an IOS-based switch, the VTP version number is configured using the following commands:
Switch# vlan database
Switch(vlan)# vtp v2-mode
Configuring the VTP Version on a CLI-Based Switch
On a CLI-based switch, the VTP version number is configured using the following command: Switch(enable) set vtp v2 enable
NOTE Many separate VTP options can be given in a single set vtp command, if desired. Consider the following example:
Switch(enable) set vtp domain mayberry mode server password opie9 v2 enable
Here, one command has set the VTP management domain name to mayberry, enabled VTP server mode, set the VTP password to opie9, and enabled VTP version 2.
VTP Status
The current VTP parameters for a management domain can be displayed. On an IOS-based switch, use the show vtp status command. On a CLI-based switch, use the show vtp domain command. Example 4-2 demonstrates some sample output of this command on a CLI-based switch.
Example 4-2 show vtp domain Reveals VTP Parameters for a Management Domain
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Switch> show vtp domain |
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Domain Name |
Domain Index VTP Version Local Mode Password |
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mydomain |
1 2 server - |
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Vlan-count Max- |
vlan-storage Config Revision Notifications |
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15 1023 |
7 disabled |
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Last Updater |
V2 Mode Pruning PruneEligible on Vlans |
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192.168.1.4 |
enabled disabled 2-1000 |
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Switch> |
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VTP message and error counters can also be displayed with the show vtp counters IOS-based command and the show vtp statistics CLI-based command. This command can be used for basic VTP troubleshooting to see if the switch is interacting with other VTP nodes in the domain. Example 4-3 demonstrates some sample output from the show vtp statistics command.
Example 4-3 show vtp statistics Reveals VTP Message and Error Counters
Example 4-3 show vtp statistics Reveals VTP Message and Error Counters
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Switch> show vtp statistics |
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VTP statistics: |
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summary advts received |
8 |
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subset advts received |
11 |
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request advts received |
0 |
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summary advts transmitted |
1 |
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subset advts transmitted |
1 |
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request advts transmitted |
0 |
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No of config revision errors |
0 |
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No of config digest errors |
0 |
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VTP pruning statistics: |
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Trunk Join Transmitted |
Join Received |
Summary advts received from |
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non-pruning-capable device |
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311 |
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Switch> |
Continue reading here: Enabling VTP Pruning on a CLIBased Switch
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