From: Scott M Vermillion (scott@it-ag.com)
Date: Fri Sep 07 2007 - 20:29:26 ART
OK all, today I see some VTP behavior that I think is in contrast with my
understanding of VTP, so I go to the DocCD > 3560 > Configuring VTP. There,
I find:
"In VTP Version 2, transparent switches do forward VTP advertisements that
they receive from other switches through their trunk interfaces."
Furthermore:
"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."
Which is consistent with my understanding of VTP operation. I am easily
able to verify the part about Ver 1 inspecting the version and domain name
before forwarding summary advertisements. As for the statement regarding
Ver 2.
My lab is simple SW1 connected to both SW2 and SW4, with each of those
connected to SW3 (the basic "diamond" you find in the Bridging and Switching
section of IEWB#1, although this is not exactly any one of the labs found
there). SW1 is the VTP server and it is running Ver 2 w/ domain name
"CISCO." SW2 and SW4 are configured for transparent Ver 2 w/ domain name
"TRANS." SW3 is configured for client and nothing more (should pick up Ver
2 from the VTP server). Everything is uncabled, vlan.dat is deleted, all
switches rebooted, everything I just mentioned configured, then everything
is cabled back up. Here, after a period much longer than the five-minute
summary advertisement interval, is what I see at SW3:
SW3#sh vtp stat
VTP Version: running
VTP1 (VTP2 capable)
Configuration Revision: 0
Maximum VLANs supported locally : 1005
Number of existing VLANs: 5
VTP Operating Mode: ClientVTP
Domain Name: VTP
Pruning Mode: Disabled
VTP V2 Mode: Disabled
VTP Traps Generation: Disabled
MD5 digest: 0x57 0xCD
0x40 0x65 0x63 0x59 0x47 0xBD
Configuration last modified by 0.0.0.0 at 0-0-00 00:00:00
SW3#
What is it about "because VTP Version 2 supports only one domain, it
forwards VTP messages in transparent mode without inspecting the version and
domain name" that I am failing to understand? I realize this is a pretty
basic question to be asking the list, but I didn't have any switches in my
lab during written prep, so I had to accept what I read without any kind of
verification where L2 was concerned. Now I'm backtracking and trying to
verify absolutely everything (hey, I invested heavily in these 3560s, I'm
not leaving one single switching point on the table in any of my lab
attempts!!). Am I just reading this totally wrong? Don't see how you
could, but I suppose it's possible.
Regards all,
Scott
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