IP Routing Features

Configuring DHCP Relay

Option 82 Field Content

The Remote ID and Circuit ID subfields comprise the Option 82 field a relay agent appends to client requests. A DHCP server configured to apply a different IP addressing policy to different areas of a network uses the values in these subfields to determine which DHCP policy to apply to a given client request.

Remote ID: This configurable subfield identifies a policy area that comprises either the routing switch as a whole (by using the routing switch MAC address) or an individual VLAN configured on the routing switch (by using the IP address of the VLAN receiving the client request).

Use the IP address option if the server will apply different IP addressing policies to DHCP client requests from ports in different VLANs on the same routing switch.

Use the MAC address option if, on a given routing switch, it does not matter to the DHCP server which VLAN is the source of a client request (that is, use the MAC address option if the IP addressing policies supported by the target DHCP server do not distinguish between client requests from ports in different VLANs in the same routing switch)

To view the MAC address for a given routing switch, execute the show system-informationcommand in the CLI.

Switch MAC Address

Figure 7-12.Using the CLI To View the Switch MAC Address

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