Configuring DHCP Relay Proxy

The DHCP relay proxy is an enhancement to the E Series router’s DHCP relay component. The DHCP relay proxy manages host routes for DHCP clients, and determines which offer to use when there are multiple DHCP servers configured.

Note: The E Series router configured as a DHCP relay proxy must be the first hop from the DHCP client. If it is not the first hop, the router defaults to the DHCP relay configuration.

You can configure a DHCP relay proxy using the following set of tasks:

Enabling DHCP Relay Proxy

Enable DHCP relay proxy and specify an IP address for the DHCP server. After you are in DHCP relay proxy mode, all set dhcp relay commands are supported.

host1(config)#set dhcp relay proxy

When you issue this command, the router adds the IP address to the list of DHCP servers (up to five) and forwards all request packets to all configured servers.

After you are in DHCP relay proxy mode, all set dhcp relay commands are supported.

Use the First Offer from a DHCP Server

You can configure the DHCP relay proxy to use the first offer it receives from any configured DHCP server and send that offer to the DHCP client. By default, DHCP relay proxy sends the most appropriate offer it receives from the configured DHCP servers to the DHCP client.

host1(config)#set dhcp relay proxy send-first-offer

Set a Timeout for DHCP Client Renewal Messages

You can set the amount of time, in the range 1–168 hours, that the DHCP relay proxy waits for a renewal message from DHCP clients after a router reboot or switchover occurs. A renewal message is required from DHCP clients when a router reboot or switchover occurs. If no renewal message is received before the timeout expires, the relay proxy declares the client no longer active and removes the client’s host route By default, DHCP relay proxy uses timeout of 72 hours.

host1(config)#set dhcp relay proxy timeout 8

Note: DHCP relay proxy does not remove a DHCP client's host route when the lease for the client's IP address expires. DHCP relay proxy will instead remove the host route when the relay proxy timeout expires. To prevent a host route from remaining long after lease expiration, modify the relay proxy timeout from its default setting of 72 hours to a setting close to, but not less than the lease time.

Related Documentation