Circuit ID
Circuit ID is a nonconfigurable subfield that
identifies the port number of the physical port through which the
routing switch received a given DHCP client request and is necessary
to identify if you want to configure an Option 82 DHCP server to use
the Circuit ID to select a DHCP policy to assign to clients connected
to the port. This number is the identity of the inbound port. On HPE
fixed-port switches, the port number used for the circuit ID is always
the same as the physical port number shown on the front of the switch.
On HPE chassis switches, where a dedicated, sequential block of internal
port numbers are reserved for each slot, regardless of whether a slot
is occupied, the circuit ID for a given port is the sequential index
number for that port position in the slot. (To view the index number
assignments for ports in the routing switch, use the walkmib
ifname
command.)
For example, the Circuit ID for port 11 on an HPE switch is “11”.
Using walkmib to determine the Circuit ID for a port on an HPE chassis
switch(config)# walkmib ifname ifName.1 = 1 ifName.2 = 2 ifName.3 = 3 ifName.4 = 4 ifName.5 = 5 ifName.6 = 6 ifName.7 = 7 ifName.8 = 8 ifName.9 = 9 ifName.10 = 10 ifName.11 = 11 ifName.12 = 12
For example, suppose that you want port 10 on a given relay agent to support no more than five DHCP clients simultaneously. You can configure the server to allow only five IP addressing assignments at any one time for the circuit ID (port) and remote ID (MAC address) corresponding to port 10 on the selected relay agent.
Similarly, if you want to define specific ranges of addresses for clients on different ports in the same VLAN, you can configure the server with the range of IP addresses allowed for each circuit ID (port) associated with the remote ID (IP address) for the selected VLAN.