IP Routing Features

Configuring DHCP Relay

Circuit ID: This nonconfigurable subfield 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 ProCurve 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 ProCurve 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 assign­ ments for ports in the routing switch, use the walkmib ifname command.)

For example, the circuit ID for a client connected to port 11 on a ProCurve 2650-PWR (J8165A) switch is “11”. However, the Circuit ID for port B11 on a ProCurve 5304xl (J4850A) is “37”. (See Figure 7-13, below.)

In this example, the 5304xl has a 4-port module installed in slot “A” and a 24-port module installed in slot “B”. Thus, the first port numbers in the listing are the Index numbers reserved for slot “A”. The first Index port number for slot “B” is “27”, and the Index port number for port B11 (and therefore the Circuit ID number) is “37”.

The Index (and Circuit ID) number for port B11 on a 5304xl routing switch.

Figure 7-13.Using Walkmib To Determine the Circuit ID for a Port on a ProCurve Chassis

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