Michael McNamara

It would seem a great many people are running into this error so I thought I would post a quick article that would help all those looking for a solution to their problem. The Nortel i2002/i2004 (any Nortel IP phone) will return the error "DHCP parse error" if the DHCP server returns DHCP option 128 with an invalid format.

In one of my first blog posts entitled "DHCP Options (VoIP)" I outlined the DHCP options and the format that the phone expected. Kenneth quickly pointed out that I had fat-fingered the example DHCP string omitting the semicolon between the values for the primary Call Server (S1) and the secondary Call Server (S2). (I've since fixed the original post)

Here's the format the DHCP option code 128 which the IP phones expects to be returned from the DHCP server when the IP phone is configured for "Full DHCP";

Nortel-i2004-A,iii.iii.iii.iii:ppppp,aaa,rrr;iii.iii.iii.iii:ppppp,aaa,rrr.

Where the following values are;

• “Nortel-i2004-A” = Option #128 begins with this string for all Nortel IP phone sets
• “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

The IP Address must be separated from the port number by a colon (:). The parameters for the Primary (S1) and the Secondary (S2) Call Servers are separated by a semicolon (;). The string must end a period (.).

If you are using an ISC DHCP server (this is generally included with any of the Linux distributions) you can refer to my article entitled "ISC DHCP Server (Nortel VoIP)" for information on how to setup and configure the ISC DHCP server to work with Nortel IP Telephony.

Cheers!