When a DHCP relay agent forwards a DHCP Discover message, it does not check whether the DHCP server status is Down. If multiple DHCP server addresses are configured on an interface, multiple DHCP servers respond with DHCP Offer messages to the DHCP client. However, the DHCP client uses the first received DHCP Offer message. As a result, IP addresses in the IP address pool on the first DHCP server are insufficient, but available IP addresses in the IP address pools on the other DHCP servers are not allocated. To make each DHCP server allocate the same number of IP addresses, a DHCP relay agent changes the forwarding order each time it forwards a DHCP Discover message, so that load balancing is implemented among DHCP servers. A DHCP relay agent forwards a DHCP Discover message as follows:

• The DHCP relay agent forwards the message to all DHCP servers by default, and changes the forwarding order each time it forwards a DHCP Discover message.
• You can configure the ip relay address cycle command to reduce the number of packets received by a DHCP server and lessen the load of a DHCP server. After this command is configured, the DHCP relay agent forwards a received DHCP Discover message to one DHCP server at a time, and forwards the DHCP Discover message to a different DHCP server each time it receives the message.