User`s manual

Moxa E Series Managed Ethernet Switch Featured Functions
3-58
The Option 82 information contains 2 sub-options, Circuit ID and Remote ID, which define the relationship
between the end device IP and the DHCP Option 82 server. The Circuit ID is a 4-byte number generated by the
Ethernet switch—a combination of physical port number and VLAN ID. The format of the Circuit ID is shown
below:
FF–VV–VV–PP
This is where the first byte “FF” is fixed to “01”, the second and the third byte “VV-VV” is formed by the port
VLAN ID in hex, and the last byte “PP” is formed by the port number in hex. For example:
01–00–0F–03 is the “Circuit ID” of port number 3 with port VLAN ID 15.
The “Remote ID” identifies the relay agent itself and can be one of the following:
1. The IP address of the relay agent.
2. The MAC address of the relay agent.
3. A combination of IP address and MAC address of the relay agent.
4. A user-defined string.
DHCP Relay Agent