7911G with 3560

Unanswered Question
May 4th, 2008

Hello, i have a 3560 switch and i want to plug a cisco ip phone 7911G and a computer.

My configuration is the following :

switchport mode access vlan 40 (data vlan)

switchport voice vlan 1 (voice vlan)

it works with other phone device (7945 and 7960) but not with the 7911G (stays blocking on "configuring ip"). When i plug a 7911G directly on a port with just the cisco voice vlan 1 without the access vlan 40 it works.

any idea?

I have this problem too.
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gogasca Sun, 05/04/2008 - 19:35

There a lot of things to check

1. In which VLAn the DHCP server resides

2. Do you see in the 7911 if we are getting the proper vlan via CDP

3. CDP is enabled?

4. If you assign static IP address it works?

Mohamed Amine Jaafar Sat, 12/07/2013 - 01:15

So, you hit this bug :


You should not use vlan 1 as voice vlan with 7906/11/31 because when the phones receive "voice vlan 1" in CDP, they will not tag their packets (instead of insisting in tagging them with VLAN ID = 1 ), and since the port is configured with an access and a voice vlan, the switchport will force tagging the untagged packets of the phone with the access vlan ID which is other than 1 (with the vlan ID 40 in the above example)

And finally the DHCP will be faulty and every other config will be so..


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