Hello,
The DHCP Relay Agent Information Option 82 is very generic in the sense that the format of the Remote ID and Circuit ID are largely arbitrary. See RFC 3046 Section 2.0 for details. Thus, there is no fixed representation or meaning to the contents of these suboptions, and according to the same RFC, there is no indication of what type of information has been inserted into them. Every vendor can put different values in there, and there is no unambiguous way of knowing what do those values represent.
Cisco Catalyst switches use the following format for Option 82 when doing DHCP Snooping:
(Retaken from Catalyst 3560 Configuration Guide.)
You can optionally force your Catalysts to use either a hostname or a user-defined string in the Remote ID suboption by means of ip dhcp snooping information option format remote-id { hostname | string ... } command.
In addition, you can redefine the Circuit ID using the per-interface ip dhcp snooping vlan information option format-type circuit-id string ... command.
So, specifically on Catalyst switches, you can redefine the Remote ID and Circuit ID to any unique values you would like to have. However, other devices and/or vendors may use their own values and their meaning. Once again, because there is nothing in the Option 82 alone that would indicate the type or format of these values, you cannot expect that your BNG/BRAS will know how to interpret them and show them nicely.
Best regards,
Peter
