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vtp pruning and tranparent switch

Hi every body!

I understand that a switch in vtp tranparent mode serves as a relay for a vtp domain. Its job is to receive and relay the vtp messages to other switches in vtp domain without applying any configurational changes to itself.

My book discusses a trouble shooting method by working out a problem.

The toplogy is there are three switches sw1,sw2 and sw3. Sw1 and sw3 are vtp server and client respectively while the sw2 is transparent mode.

All switches are connected in triangular fashion.

The problem was that vlan 3 was not being forwarded on trunk between sw1 and sw2.

Here is what my book says while ruling out vtp pruning being a problem:

"Vtp pruning can be ruled out because earlier examples showed all three switches have atleast one interface in vlan 3 and in connect state."

The important terms in the above excerpt are " all three switches" which include sw2 ( transparent mode).

The book is implying sw2 ( transparent mode) can participate in vtp pruning.

==========================

All this comes down to one question Does a switch, in transparent mode participate in vtp pruning when the command " vtp pruning is enabled on the vtp server switch ?

thanks a lot and have a nice day!

1 ACCEPTED SOLUTION

Accepted Solutions
Hall of Fame Super Silver

Re: vtp pruning and tranparent switch

Hello Sarah,

in order for vlan3 to travel on the switch chain given the transparent role of sw2:

sw1---sw2--sw3

sw2 has to define vlan 3 in local database and to permit it on trunk links to sw1 and sw3.

A useful document about VTP troubleshooting is here:

http://www.cisco.com/en/US/tech/tk389/tk689/technologies_tech_note09186a0080890613.shtml

Now, in theory messages from server VTP sw1 can flow from left to right and messages from sw3 to sw1 can flow from right to left.

This is my understanding of VTP transparent mode.

It should not take part in VTP pruning.

So a possible reason for a partitioned vlan3 topology is that is missing in the list of permitted vlans on one port of sw2 for example.

Hope to help

Giuseppe

2 REPLIES
Hall of Fame Super Silver

Re: vtp pruning and tranparent switch

Hello Sarah,

in order for vlan3 to travel on the switch chain given the transparent role of sw2:

sw1---sw2--sw3

sw2 has to define vlan 3 in local database and to permit it on trunk links to sw1 and sw3.

A useful document about VTP troubleshooting is here:

http://www.cisco.com/en/US/tech/tk389/tk689/technologies_tech_note09186a0080890613.shtml

Now, in theory messages from server VTP sw1 can flow from left to right and messages from sw3 to sw1 can flow from right to left.

This is my understanding of VTP transparent mode.

It should not take part in VTP pruning.

So a possible reason for a partitioned vlan3 topology is that is missing in the list of permitted vlans on one port of sw2 for example.

Hope to help

Giuseppe

Re: vtp pruning and tranparent switch

hi sarah

i have seen a case like this

sw2 -- sw3 -- sw4 vlan 5 - - L3-vlan5-sw2

R1--vlan 5--sw3---

sw3 trasparant

we have vlan lets say vlan 5 create in all swithes

R1 connected to sw3 vlan 5 and cmmunicate with switch 2 routed interface that connected to sw4 in vlan 5

i know it looks confusing

but here you will run in losing connectivity unless you remove pruning of vlan 5 in the tunk linke between sw3 and sw4

beucase SW3 is in VTP transparent mode it does not

participate in VTP and will only pass on VTP pruning messages between the

other switches

HTH

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