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Community Member

DHCP on 3560

We are implmenting VoIP in one of the center where we have configure DHCP server on 3560. We are using Nortel VoIP phones and we need to set option 128 and 191. I am looking for help as how we can set these option on cisco 3560 switch DHCP. Thanks in advance.


Re: DHCP on 3560

Essentially under your dhcp scope you can configure these options just by typing options and your option number with the IP.

Hope this helps

Excerpt from the above doc

option code [instance number] {ascii string | hex string | ip-address}


Router(dhcp-config)# option 19 hex 01

Community Member

Re: DHCP on 3560

I have gone through this and not clear exact config as i am not sure what these [instance number] {ascii string | hex string | ip-address} stand for.I am reffreing below document extract for configuration of DHCP for Nortel Phone

The format of the String for the 128 Site Specific Option is:


Where “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

The Site Specific Option #191

Where: “A” = Hardware Revision of the i2004 IP Phone

“vvvv”= The VLAN ID in Decimal



Re: DHCP on 3560

Unfortunately I am not well versed on the nortel side.

I would try this though

option 191 ip x.x.x.x

and see if your nortel phones pick that up.

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