3750 voice vlan problem

[l-mathews]

Hello All,

I have an issue on the Cat 3750 on the voice vlan; IP Phone not registering with PBX & Signaling Server.  The ip phone hits dhcp and gets an ip address

from a data scope. Data scope does have dhcp options for voice, same as voice scope so it should work but it doesnt.

We removed the switchport access vlan 50 command, and left the switchport access voice vlan 51, and now the phone registers.

Anything I can check on the switch to make sure voice vlan is working? Any debug voice vlan commands?

The switch doesnt seem to distinguish voice and data traffic.

I check dhcp and both scopes vlan 50 and vlan 51 have the same configuration.  Defautl GW is different of course

Catalyst 3750 is running 12.2(25)SEE2

Here is sample config

interface FastEthernet4/0/12

switchport access vlan 50

switchport mode access

switchport voice vlan 51

switchport port-security maximum 5

switchport port-security aging time 5

switchport port-security violation restrict

switchport port-security aging type inactivity

speed 100

duplex full

snmp trap mac-notification added

snmp trap mac-notification removed

spanning-tree portfast

spanning-tree guard root

ip dhcp snooping limit rate 10

[d.tobin]

What kind of IP phone are you using?  If it doesn't support CDP you will need to enalbe LLDP on your switch for the phone to discover the voice vlan.

[l-mathews]

The ip phones are nortel 1120E, but there are others Nortel IP Phones (IP 2007) that have this issue.

I am focusing on the 1120Es.

The switches dont support lldp command, but the phones do. LLDP is enabled on the phone but that doesnt do any good

because the switch doesnt support. Not unless I upgrade the code

The ip phones were working without lldp up until now, why all of a sudden does it need it? (I agree with using lldp, going forward but not the root cause of the problem)

[Leo Laohoo]

I think I've seen phones like this before.  You need to enable dot1q trunking (allow data and voice VLAN) and leave the voice VLAN configuration.

[l-mathews]

dot1q trunking is enabled on the ip phone. As with the previous reply, not a bad suggestion but why did all 100+ ip phones work without dot1q trunking configured on the switch up until now.

Update

We moved one of the bad ip phones to a different stack of 3750s, and the problem didnt appear.

IP Phone registered, and got an ip from voice scope/subnet/vlan vlan 51. Moving the phone back to original stack, didnt bring back the problem either. ip phone still registered, came up and had ip from voice scope/subnet/vlan vlan 51.

In addition,

On original stack of 3750s I reconfigured the ip phone and its 8021q trunking (enabled by default), and I specified

the voice vlan id (51), and the data vlan id (50), and disabled LLDP.
I tested each individual command separately, and each didnt work by themselves, However, all 3 (configure concurrently) worked.

Rolled back each command to see if the problem reappeared, and it didnt.

[l-mathews]

Also,

both 3750 stacks are runningn same ios code 12.2 (25)SEE2.