Problem with VLANs

[v_tigin85]

Hello there, first off I would like to wish you all a very Merry Christmas.

We have the following setup (refer to diagram 1). On the Catalyst 2950, port 6 is taken up by a DHCP server, and port 7 is taken up by a Cisco CallManager server. On the Catalyst 3560G we have several Cisco phones (Example config provided). The Cisco Catalyst 3560G is connected via an optical SFP to another 3560 at a remote site, all of the ports at that site are configured as shown.

Now the problem is the following, none of the ports on the Cisco 3560 at the remote site can see the DHCP server on the Cisco 2950, nor can they get to the CallManager. STP output from the remote site shows that that device is root of VLAN 20 and VLAN 1000, the STP output from the core switch (C3560G) shows that it is also the root of all VLANs.

VTP mode of the C3560G and C2950 is server and the VTP mode of the remote site is client. I'm not sure whether this helps matters or not.

Judging from the STP output from the core switch, it would seem that the VLAN information is not forwarded to the SFP port.

Also, the Cisco Phones at the remote site seem to be able to get a DHCP lease from their respective DHCP server, but they cannot seem to reach CallManager.

Any help would be greatly appreciated, thank you in advance!

[glen.grant]

I would check your trunking parameters between the switches , sounds like something is not right . Maybe you can post the 2950 and 3560 configs and we could spot something. If you do a "show trunk " on both switches do the uplinks look right ??

[Georg Pauwen]

Hello,

merry Christmas to you, too.

Looking at your diagram, and keeping in mind that both 3560 switches declare themselves as root, I wonder if the VTP works between the switches. Can you verify that both 3560s are actually configured with the same VTP domain (case-sensitive) and are running the same VTP version ?

Also, try and manually set the 3560 directly connected to the 2950 as root with the command:

spanning-tree vlan X priority 0

Also, set the 2950 to VTP client mode.

Can you try this and see if it makes a difference ?

Regards,

GP

[yasirirfan · Accepted solution]

Hi Tigin

Meery Christmas,

Looking at your scenario I would recommend you to make following things

1) Create a VTP domain (name it any thing for eg cisco)

2) Then make 3560 G switch VTP mode server and domain cisco

3) Other tow switches will be VTP mode client and domain cisco.

4) use this command switch port trunk for the gigabit interfaces connecting 3560 and 2950 from 3560 switch.

Make sure you have the same encapsulation in all swicthes and VTP version to remains same.

Do this and if u need any further assistance contact me.

Cheers

Yasir

[v_tigin85]

Thank you all very much for your help, the problem was solved by forcing the SFP ports into trunking mode.

[yasirirfan]

Hi Tigin

Its great it solved ur problem