Figure 123 A Multiple VTP Domain Network

Whenever a Catalyst makes a VTP announcement, it includes the VTP domain name. If the receiving Catalyst belongs to a different management domain, it ignores the announcement. Therefore, VTP announcements from the wally domain on the left of the drawing are never seen by the Catalysts in the wally domain on the right of the drawing.

If you are installing a domain border switch that connects two domains, it becomes a member of the management domain that it first hears from. Therefore, be sure to attach it to the domain that you want it to belong to first. Make sure that it acquires the VTP domain name, and then attach it to the other domain. Otherwise, you need to manually configure the domain name.

Warning

A side effect of VTP domains can prevent an ISL trunk link from negotiating correctly with dynamic ISL (DISL). When DISL initiates trunk negotiation, it includes the VTP domain name in the message. If the two ends of the link belong to different domains, the trunk fails to establish automatically. To enable a trunk on border Catalysts between domains, set both ends of the trunk to ON or nonegotiate.

VTP Modes

Referencing the set vtp ? output of Example 12-2, notice that you have the option to configure a VTP mode. You can configure VTP to operate in one of three modes:

server, client, or transparent. The three modes differ in how they source VTP messages and in how they respond when they receive VTP messages. Table 12-2 summarizes the differences between the three modes.

Table 12-2. VTP Mode Comparisons

Feature

Server

Client

Transparent

Source VTP Messages

Yes

Yes

No

Listen to VTP Messages

Yes

Yes

No

Create VLANs

Yes

No

Yes*

Remember VLANs

Yes

No

Yes*

*Locally significant only.

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