Hi Yevgeniy,
DHCP Option 82 stands for “DHCP Relay Agent Information Option”. If you haven’t seen how DHCP relay works before, take a look at this lesson:
Option 82 was originally created for really large (WAN) networks where we have a lot of DHCP relays and central DHCP servers. The idea behind it is that the DHCP relay can add extra information which the DHCP server can use to decide which pool to use for assigning an IP address. Option 82 has a “Circuit ID” and a “Remote ID”.
The Circuit ID has information that identifies the port where the request came from. It could carry something like:
Router interface number
VLAN information
Switching Hub port number
Remote Access Server port number
Frame Relay DLCI
ATM virtual circuit number
Cable Data virtual circuit number
The remote ID adds information about the DHCP relay, it could contain something like:
Caller ID (telephone number) for dial-up connections.
username
modem ID
remote IP of point-to-point link
Option 82 is decribed in RFC 3046 in 2001 so it’s quite old. It’s not used often on (small) LAN networks.
Does this help a bit? Maybe I should do a proper lesson for option 82 with some debugs etc.
Rene