I hope that some one can explain the behavior of VTP on Cisco 5505
switches.
I have two Cisco 5505 switches, S1 running version 4.2.2 and S2 running
4.5.4. All ports on S1 assigned to VLAN 10, except ports 1/2 and 2/23
which are trunk ports. All ports on S2 are assigned to VLAN 11, except
ports 1/2 and 2/23 which are trunk ports. The two trunk ports 2/23 on
both switches are connected to two 2621 routers. The two two trunk ports
1/2 on both switches are interconnected by MMF cable, but the port on S1
is logically disabled so that the two switches can not communicate with
each other.
set vtp domain xyz
set vtp mode server
have been configured on both switches.
All the four trunk ports are configured for ISL with VLANS 1,10 and 11
only. However when I do a "sh trunk" on S1 it says that the trunk on
port 2/23 has VLANS 1,10-11 available, but only VLANS 1 and 10 are
active. When I execute the same command on S2, it says that VLANS 1 and
11 are active and available on trunk for port 2/23.
Basically S1 did not know anything about VLAN 11 and S2 did not know
anything about VLAN 10.
The idea is to run HSRP between the two routers so that if any one
router fails, all devices attached to both switches will be able to
communicate to the outside via the remaining router.
This requires that traffic should flow between the two switches and each
switch must be aware of both VLANs 10 and 11.
After making sure that the VTP version number was zero on both switches,
on a fateful morning, at 4 am, I enabled remotely the trunk on 1/2 port
on S1 so that the link between the two switches became active. To my
utter dismay, S2 promptly and completely shut itself down and I could
not communicate with it. I drove to my office to pick up my laptop and
drove to the remote location to find out what had happened.
All non-trunked ports were in an "inactive" state in S2. Apparently when
S2 received the VTP advertisement from S1 and did not see VLAN 11 in it,
S2 rendered inactive all ports assigned to VLAN 11. But both S1 and S2
are in "server" mode! Why did this happen? This behavior is typical when
there is a revision level mis-match and a "client" mode switch receives
an update with a higher revision number and missing VLAN definitions.
Cisco TAC says that there should be only one server in any VTP domain. I
don't believe that.
TAC also said that a better method would be to configure both switches
in transparent VTP mode.
Any ideas?
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