40An Introduction to IP Routing Protocols

"DHCP operation" (page 40)Figure DHCP operation shows an end station connected to subnet 1, corresponding to VLAN 1. The Nortel Ethernet Routing Switch 5500 Series connects two subnets by means of the virtual routing function. When the end station generates a DHCP request as a limited UDP broadcast to the IP address of all 1s (that is, 255.255.255.255) with the DHCP relay function configured, the Nortel Ethernet Routing Switch 5500 Series forwards DHCP requests to subnet 2 or to the host address of the DHCP server, depending on the configuration.

DHCP operation

Forwarding DHCP packets

In the example shown in "Forwarding DHCP packets" (page 40), the agent address is 10.10.1.254. To configure the Nortel Ethernet Routing Switch 5500 Series to forward DHCP packets from the end station to the server, use 10.10.2.1 as the server address.

Forwarding DHCP packets

All BootP broadcast packets, including DHCP packets that appear on the VLAN 1 router interface (10.10.1.254), will be forwarded to the DHCP server. In this case, the DHCP packets are forwarded as unicast to the DHCP server’s IP address.

Multiple BootP-DHCP servers

Most enterprise networks use multiple BootP/DHCP servers for fault tolerance. The Nortel Ethernet Routing Switch 5500 Series allows switch configuration to forward BootP/DHCP requests to multiple servers. Up to 10 servers can be configured to receive copies of the forwarded BootP/DHCP messages.

Nortel Ethernet Routing Switch 5500 Series

Configuration-IP Routing Protocols

NN47200-503 03.01 Standard

5.127 August 2007

Copyright © 2005-2007, Nortel Networks

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Nortel Networks NN47200-503 manual Forwarding Dhcp packets, Multiple BootP-DHCP servers, Dhcp operation