Cisco Ip phone problem over switch trunk

Unanswered Question
Sep 1st, 2007

We have cisco cat 3750 with Ip phones configured on some ports as below..frequently these phones 76x do not acquire addresses or do not work...(ip helper address configured on SVI)..could anyone guide as to how to go about troubleshooting what could be causing this often solves by resetting the native VLAN( we cannot use aux vlan config in this environ just yet)

switchport access vlan xxx

switchport trunk encapsulation dot1q

switchport trunk native vlan xxx

switchport trunk allowed vlan yyy,xxx

switchport mode trunk

speed 100

duplex full

Pointers appreciated

I have this problem too.
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mchandak Sat, 09/01/2007 - 10:17

Can you confirm that you have configured VLAN, Speed and Duplex on the phone ??

mchandak Sat, 09/01/2007 - 12:19

Rob, to answer this Mahesh, the reason it is not mentioned is coz the Post states:

( we cannot use aux vlan config in this environ just yet)

So, with the aux/voice vlan not being an option, we need to do a Manual config :-)

maheshbalasub75 Sat, 09/01/2007 - 20:49

Yes the same have been configured ...just would like to know how to go about troubleshooting the same as everytime it starts working after resetting the native VLAn to some oher VLAN and then back to old native VLAn and Lo it starts working

And yes we cannot use voice Vlan in this etup as yet

Thanks and regards

karunanithi Mon, 09/03/2007 - 00:48


For troubleshooting, you can try configuring Voice VLAN as a access VLAN and see whether Phones are taking the IP address, with the above configuration give static IP.



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