AVAYA Can't Get DHCP Address with Cisco 2960

[chenran]

We recently experienced an issue on AVAYA 1608i DHCP assignment issue.

We have a DHCP server on Fornite with VLAN 20(10.20.20.0 ).

Switch uplink was configured with trunk with the allowed pass of multiple VLAN including VLAN20

Phone connected port on the switch (2960) was configured with non-voice VLAN 20. Under this configuration, 1608i was unable to get IP from the DHCP pool. Beside, switch can't learn its mac address as well. Once we changed the port to switch port voice VLAN 20, it 'll get an IP address right way.

My question would be why 1608i can't get DHCP address under non-VOICE VLAN configuration, thanks.

[Georg Pauwen]

Hello,

the 'switchport voice vlan 20' command makes sure that traffic for Vlan 20 is tagged. If you configure Vlan 20 as a 'normal' access port, the traffic is untagged. Your phone needs to see tagged traffic, that is probably why it doesn't work with the untagged access port.

[chenran]

Hi Georg, thanks for your reply.

FYI, our current port configuration(working properly):

switchport voice vlan 20

switchport mode access

With listed configuration, Phone can't get DHCP address(not working):

switchport access vlan 30
switchport mode access
switchport voice vlan 20

Are you suggest we make it VOIP VLAN port without configuring it as access port like below:

switchport voice vlan 20

switchport access vlan 30

How about if we want to connect a PC to the IP phone ?

Does missing switchport mode access under port configuration matter? 

[Georg Pauwen]

Hello,

the Avaya phones might work differently. Try to configure the port as a trunk port, with the voice Vlan being the native Vlan:

switchport trunk encapsulation dot1q
swicthport trunk allowed vlan 20, 30
switchport trunk native vlan 20

[Thomas Schmitt]

May be this is LLDP-MED issue? The phone expects a voice VLAN announcement to begin with DHCP

[pieterh]

in your post I see you mention both:

- non-voice VLAN 20
- switchport voice vlan 20

VLAN20 is either the voice vlan or it is not!

A voice vlan is a SECOND vlan used on an access port  (not a vlan trunk port),

it is intended to be automatically discovered by an IP phone

the desired port config for phone in vlan20 and workstation in vlan 30 would be:

     switchport access vlan 30
     switchport mode access

in addition with

     switchport voice vlan 20

Cisco phones use CDP to discover the voice-vlan, other phones will use LLDP for this, maybe you need to enable LLDP?

otherwise you may need to distribute the voice vlan using DHCP-options.

NB! also check if you have a DHCP-server/scope  for both vlan's