Switch User Manual

40 An 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 Ser ies 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 enterpr ise 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

5.1 27 August 2007