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Vlan Trunking.

We currently are under going some infrastructure changes.

We had been running a core switch for 300+ users on a 2948-G, we recently upgraded all the closets and server racks to a 4503. We still have a couple of switches branched off the old 2948. One of those brached off is a Cat3524. On the 2950 I have an IP phone, the phone is in vlan 10 and the remainder of the ports are in vlan 20. trunking is enabled and all is woking well on that switch.

Now I also have an IP phone on a 3524. All client/closet switches are set to vtp client and the proper vtp domain is being used. From that point on the 3524 is not pulling down any of the vlan info from the server. I also am having problems taking port 24 on the 3524 to port 47 on the 2948 and trunking the connection . If I do that and assign the IP phone on port 2 to vlan 10 of the 3524. 1. It cannot make the connection and 2. I takes the network to its knees.

Is the 3524 capable of being in vtp client and pulling down the vlan info? Is it possible to trunk between 2 client switches?

I want to get the 3524 off the 2948 and into the 4503 (actually I want to get the 3524 off the floor and in the trash) but we require 24x7x363 uptime on the servers connected to it. We only have 2 days a year were we are allowed to bring the servers down for maintenance. I am a little gun shy doing this becasue I already dropped the connections 3 times in one week trying to get this to work. I cant drop it again.

I can post configs if needed, but I am home and do not have access to them right now.




Re: Vlan Trunking.


1) I think your basic problem might be trunking between 3524 and 2948.

If you check on your 3524:

sh int fa 0/24 sw

do you see

Operational Mode: trunk

Operational Trunking Encapsulation: dot1q ?

Are you running CatOS on your 2948G?

If yes, is sh trunk command showing port 47 as trunking?

Here are links how to configure trunks on Cat2948Gs running CatOS:

and on CAt3524 running IOS:

But be careful - enabling/disabling trunking on the port can reset the port and the servers connected to the switch might lose their connectivity.

2) If the trunk connection is working OK, there should be no problem with VTP getting info from the neighboring client switch.

But the trunk MUST be up first (VTP works ONLY on trunks, VLAN1 must be allowed on the trunk).

sh vtp status command will show you if 3524 is using correct VTP domain, version, etc.

Check the Configuration Revision number and Configuration last modified...

items to see if 3524 is receiving correct VTP info from the neighbor.

sh vlan will also list all VLANs configured on the 3524 so you can see again if VTP works correctly.



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