This took longer to track down via google than it should have when I was looking. So here it is simple and to the point for running Nortel IP Phones with cisco DHCP:
dhcpd option 128 ascii Nortel-i2004-A,220.127.116.11:4100,1,1;18.104.22.168:4100,1,10. interface inside
I used examples of s1: 22.214.171.124 and s2: 126.96.36.199 Of course your IPs will substitute there.
One thing to note, if you have a certain model of Nortel system (or have changed the listening port on yours) the 4100 in the command will of course be a different port...
here's the syntax:
“A” = the Hardware Revision of the i2004 Phone
“iii.iii.iii.iii” = the IP Address of the Call Server (S1 or S2)
“ppppp” = port number for the Call Server
“aaa” = the Action for the Server
“rrr” = the Retry Count for the Server