[c-nsp] option 82

MKS rekordmeister at gmail.com
Mon Dec 8 18:27:50 EST 2008

Hi list

I'm trying to find information about how cisco formats the option 82
field in DHCP
So far I got this

"Type		         Format type. The value 2 specifies the format for use
with this feature. (1 byte)
Length	          	Length of the Agent Remote ID suboption, not
including the type and length fields. (1 byte)
Reserved 	         Reserved. (2 bytes)
NAS IP Address	IP address of the interface specified by the ip
unnumbered command. (4 bytes)
Interface	Physical interface. This field has the following format:
		slot (4 bits) | module (1 bit) | port (3 bits).
		For example, if the interface name is interface ethernet 2/1/1, the
slot is 2, the module is 1, and the port is 1. (1 byte)

Reserved	Reserved. (1 byte)
VLAN ID		VLAN identifier for the Ethernet interface. (2 bytes)

and this
"The option 82 format may vary from product to product. Contact the
relay agent vendor for this information. "

I'm specifically looking for info in decoding option 82 in cisco 7600
on ethernet interfaces and 7200 on atm interfaces.

If somebody can point me the right direction that would be great, else
I have to go through tac...


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