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VTP adv. not transiting a transparent switch in diff. domain

In cisco documentation

http://www.cisco.com/en/US/tech/tk389/tk689/technologies_tech_note09186a0080890613.shtml#topic3

It states that " A switch that is in VTP transparent mode and uses VTP V2 propagates all VTP messages, regardless of the VTP domain that is listed."

I have tried this out , but I not able to pass on vtp advertisement generated from a switch(SW3) in domain CISCO123 to transit through a switch(SW1) in domain juniper(transparent) to a switch(SW2) in domain CISCO123.

The error received on SW1 (The transparent and different domain switch ) is

"00:49:33: VTP LOG RUNTIME: Dropping packet received on trunk Fa0/13 - not in domain CISCO123"

All are manually trunked.

(Client, CISCO123)SW3----(Transparent,juniper)SW1----SW2(Server, CISCO123)

1 ACCEPTED SOLUTION

Accepted Solutions

Re: VTP adv. not transiting a transparent switch in diff. domain

Ahmed,

After i've reviewed my old notes, i've made sure that this is practically not correct, plus please read the following paragraph from Cisco DocCD, according to this paragraph and the other one you've posted earlier, the words are fuzzy and full of contradictions, but my conclusion is that VTPv2 should't check the domain name, but since it only supports one domain name, thus the resultant would be that the transparent switch won't relay the VTP messages in this scenario.

"Version-Dependent Transparent Mode-In VTP version 1, a VTP transparent switch inspects VTP messages for the domain name and version and forwards a message only if the version and domain name match. Because VTP version 2 supports only one domain, it forwards VTP messages in transparent mode without inspecting the version and domain name."

http://www.cisco.com/en/US/docs/switches/lan/catalyst3550/software/release/12.1_13_ea1/configuration/guide/swvtp.html#wp1035121

What bothered me is that both cases gives the same debug output (debug sw-vlan vtp packets):

VTP LOG RUNTIME: Dropping packet received on trunk Fa0/1 - not in domain CISCO

BR,

Mohammed Mahmoud.

6 REPLIES

Re: VTP adv. not transiting a transparent switch in diff. domain

Hi,

Are you sure that all the switches are connected via trunks and not access ports and all are running VTPv2.

BR,

Mohammed Mahmoud.

New Member

Re: VTP adv. not transiting a transparent switch in diff. domain

Yes,

Sorry i was editing the link when you posted.

I added the trunking information. They are all ISL trunk links.

Re: VTP adv. not transiting a transparent switch in diff. domain

Hi Ahmed,

No problem, i believe that i've seen this behavior before and did a lot of debugs, and concluded that the documents says that this is doable, but practically its not, please let me dig it for you in my old docs.

BR,

Mohammed Mahmoud.

Re: VTP adv. not transiting a transparent switch in diff. domain

Ahmed,

After i've reviewed my old notes, i've made sure that this is practically not correct, plus please read the following paragraph from Cisco DocCD, according to this paragraph and the other one you've posted earlier, the words are fuzzy and full of contradictions, but my conclusion is that VTPv2 should't check the domain name, but since it only supports one domain name, thus the resultant would be that the transparent switch won't relay the VTP messages in this scenario.

"Version-Dependent Transparent Mode-In VTP version 1, a VTP transparent switch inspects VTP messages for the domain name and version and forwards a message only if the version and domain name match. Because VTP version 2 supports only one domain, it forwards VTP messages in transparent mode without inspecting the version and domain name."

http://www.cisco.com/en/US/docs/switches/lan/catalyst3550/software/release/12.1_13_ea1/configuration/guide/swvtp.html#wp1035121

What bothered me is that both cases gives the same debug output (debug sw-vlan vtp packets):

VTP LOG RUNTIME: Dropping packet received on trunk Fa0/1 - not in domain CISCO

BR,

Mohammed Mahmoud.

New Member

Re: VTP adv. not transiting a transparent switch in diff. domain

yeah,

Both VTP versions give the same log error. Looks like they are both discarding the different domain vtp advertisements and hence even V2 also inspects vtp messages for domain.

I was thinking that this might be a problem with the VTP domain being advertised in the DTP packets. Even in Switchport trunk mode on, dtp messages are exchanged. This COULD be a reason for this.

Re: VTP adv. not transiting a transparent switch in diff. domain

Ahmed,

Yes, first i though it is DTP, but even if you used ON trunking, and disabled DTP via "switchport nonegotiate" nothing changes.

BR,

Mohammed Mahmoud.

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