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Day: January 4, 2012

CCIE: VTP or not to VTP, that is the question.

CCIE: VTP or not to VTP, that is the question.

In *most* productions networks device limitations (VLAN,TCAM entries) must be taken into consideration. This is one of the downsides of using VTP. All switches will get the entire database regardless if they have local assignments or even are in the transit L2 path. Transparent mode and manually creating the necessary VLANs may be your best option. Switches to not create a STP instance for unnecessary VLANs thus conserving resources and CPU cycles. If you are using VTP be sure to enable pruning to conserve bandwidth or statically remove unnecessary VLANs from the trunk links. “sh interface pruning” or “sh interface trunk | begin pruned” to verify.

Two quick ways to view port/vlan assignment.

“sh vlan brief” or “sh interface status”

VTP can save time by allowing a central place to manage and create VLANs. Here are some tips when implementing VTP.

1) Make sure your trunk (ISL/.1q) interfaces are healthy.

2) Assign a domain name on the VTP server. All other clients will inherit this.

3) Create VLANs on server and verify creation/revision sync on clients.

Verify with “sh vtp status” and if a password is configured “sh vtp password”.

Transparent mode switches will pass updates but not accept them. Their revision number should be “0”.

"Sh interface trunk" can help determine the L2 transit path if the VLAN exists. This helps with tasks that required you to restrict the VLAN's allowed on trunks. 

Investigate pruning elegiable list (except/all/none). "sw tr prun vlan"