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dathaide
Beginner

VTP pruning with transparent switch in the middle

hi

I have three switches A-B-C. A is the server and B & C are clients. They are connected via trunk links. All switches are running VTP version 2. I converted Switch B to transparent and changed the vtp domain name to be different from the other two.

Issue # 1 According to Cisco doc I should be able to add a vlan on switch A and it propagate to Switch C thru the transparent Switch B in version 2. It's not happening until i make the vtp domain name on switch B the same?

Issue #2 - Back to the scenario where A-B-C are in the same vtp domain and switch A is the server and B and C are clients. I have devices off Vlan 15 off Switch A and C. I enabled pruning and see the expected results which are since traffic is requested by C it is not pruned on the trunk link from towards C. Now i change the middle switch B to transparent. I expect to lose reachability from the device connected to VLAN 15 on Switch A to the device connected to VLAN 15 on C as the middle switch is transparent. however i still have connectivity. Accoring to Cisco DOC i am to remove VLAN 15 from the prune list on the link connected to B for reachability. But it works even without me doing this step. The switches are 3560's.

Sorry for the long post but i have spent a lot of time trying to figure this out

http://www.cisco.com/en/US/docs/switches/lan/catalyst3560/software/release/12.2_40_se/configuration/guide/swvtp.html#wp1072526

4 REPLIES 4
bvsnarayana03
Contributor

Issue#1: Transparent switches forward the vtp advertisements irrespective of the domain they are in.

Issue#2: This proves the above concept.

Thanks for replying

Have to disagree with your conclusion to Issue #1. I have it lab'd up of different sets of equipment and arrived a the same conclusion that VTP advertisements will not propagate if domain names are different even in version 2.

Issue #2 - Then why does Cisco suggest when one configures vtp pruning with a transparent switch in the picture the upstream switch needs to manaully NOT prune the vlans thru the transparent switch. It works without even doing that.

Thanks

Hi Dwayne,

My understanding of vtp was the same as your's until i came across a discussion on this forum sometime ago.

You may want to check the vtp version on transparent switch, is it v2 as well?

Refer this link:

http://forum.cisco.com/eforum/servlet/NetProf?page=netprof&forum=Network Infrastructure&topic=LAN, Switching and Routing&CommCmd=MB?cmd=display_location&location=.2cbe7b75

bvsnarayana03
Contributor

Issue#1: Transparent switches forward the vtp advertisements irrespective of the domain they are in.

Issue#2: This proves the above concept.