Here’s a sample configuration detailing how to configure a Cisco router as a DHCP server for Avaya (formerly Nortel) IP phones including the Avaya/Nortel specific DHCP options 128 and 191. I thought I would share this information with the Nortel/Avaya users in case they are utilizing (or wish to utilize) the DHCP server functionality built-in to the Cisco IOS platform. The key is to configure the Cisco router to reply with the correct DHCP vendor options so the IP phone will boot properly.

!
no aaa new-model
!
ip routing
ip subnet-zero
no ip source-route
no ip finger
no ip domain-lookup
ip cef
!
!
!### 1) SET UP EXCLUSIONS FOR STATIC IP DEVICES ###
!### START ADDRESS (SPACE) END ADDRESS ###
!
!### VLAN2 DATA EXCLUSIONS ###
ip dhcp excluded-address 10.10.10.1 10.10.10.30
ip dhcp excluded-address 10.10.10.200 10.10.10.254
!
!### VLAN701 VOICE EXCLUSIONS ###
ip dhcp excluded-address 192.168.1.1 192.168.1.30
ip dhcp excluded-address 192.168.1.200 192.168.1.254
!
!### VLAN702 VOICE EXCLUSIONS ###
ip dhcp excluded-address 192.168.2.1 192.168.2.30
ip dhcp excluded-address 192.168.2.200 192.168.2.254
!
!
!### 2) SET UP DHCP FOR FOR DATA VLAN/SUBNET ###
!
ip dhcp pool Nortel_Data_VLAN2
network 10.10.10.0 255.255.255.0
default-router 10.10.10.1
option 128 ascii Nortel-i2004-A,192.168.1.21:4100,1,10.
option 191 ascii VLAN-A:701+702.
!
!
!### 3) SET UP DHCP FOR FOR VOIP-PHONES VLAN/SUBNET ###
!
!
ip dhcp pool Nortel_Voice_VLAN701
network 192.168.1.0 255.255.255.0
default-router 192.168.1.1
option 128 ascii Nortel-i2004-A,192.168.1.21:4100,1,10.
option 191 ascii VLAN-A:701+702.
!
!
ip dhcp pool Nortel_Voice_VLAN702
network 192.168.2.0 255.255.255.0
default-router 192.168.2.1
option 128 ascii Nortel-i2004-A,192.168.1.21:4100,1,10.
option 191 ascii VLAN-A:701+702.
!
!
!
!### 4) SET UP INTERFACES ###
!
!
interface fast 0/0
description ### VLAN TRUNK & ROUTE LINK TO LAN SWITCH ###
no ip address
speed 100
full-duplex
no shutdown
!
!
int fast 0/0.2
desc ### VLAN 2 DATA SUBNET ###
ip add 10.10.10.1 255.255.255.0
no ip red
no ip dir
no shut
!
int fast 0/0.701
desc ### VLAN 701 VOIP PHONES SUBNET ###
ip add 192.168.1.1 255.255.255.0
no ip red
no ip dir
no shut
!
!
int fast 0/0.702
desc ### VLAN 702 VOIP PHONES SUBNET ###
ip add 192.168.2.1 255.255.255.0
no ip dir
no ip red
no shut
!
ip route 0.0.0.0 0.0.0.0 10.10.10.254 name DEFAULT-ROUTE
!

Cheers!
Alex

-Editor, Thanks to Alex for writing this post and allowing me to re-post it here. -Michael