VLAN Configuration Rules

This page describes the configuration rules you need to follow when adding or modifying VLAN Trunk Protocol (VTP) VLANs.

Web-based switch management software does not perform VLAN database consistency checks when you create VLAN configurations with VTP V2 mode disabled. As a result, you can incorrectly set VLAN parameters that the software discovers only when you unsuccessfully try to reenable VTP V2 mode. To resolve these configuration errors, you must review the entire VLAN database and modify the incorrect configuration.

Configuration errors can occur when:

VTP V2 Mode Enabled

When VTP V2 mode is enabled and you are configuring Token Ring concentrator relay function (TRCRF) media, follow these rules:

Specify a parent VLAN ID of a Token Ring bridge relay function (TRBRF) that already exists in the database.
Specify a ring number. Do not leave this field blank.
Specify unique ring numbers when TRCRF VLANs have the same parent VLAN ID. Only one backup concentrator relay function (CRF) can be enabled.

When VTP V2 mode is enabled and you are configuring VLAN media other than TRCRF, do not specify a backup CRF. This rule applies when you enter commands through the command-line interface (CLI).

When VTP V2 mode is enabled and you are configuring a TRBRF media, you must specify a bridge number.

VTP V2 Mode Disabled

When VTP V2 mode is disabled, no VLAN can have an STP type set to AUTO. This rule applies to FDDI-NET and Token Ring-NET VLANs when you are using web-based switch management software.

Note: When you use the CLI to configure VLANs, this rule applies to Ethernet, FDDI, FDDI-NET, Token Ring, and Token Ring-NET VLANs.

Translational Bridging

When configuring a VLAN that requires translational bridging (values are not set to zero), you must follow these rules:

The translational bridging VLAN IDs that are used must already exist in the database.
The translational bridging VLAN IDs that a configuration points to must also contain a pointer to the original VLAN in one of the translational bridging parameters (for example, Ethernet points to FDDI, and FDDI points to Ethernet).
The translational bridging VLAN IDs that a configuration points to must be different media types than the original VLAN (for example, Ethernet can point to Token Ring).
If both translational bridging VLAN IDs are configured, these VLANs must be different media types (for example, Ethernet can point to FDDI and Token Ring).