Switch User Manual

IP routing 21

Step Action

Enable IP routing globally.

Assign an IP address to the speciﬁc VLAN or brouter port.

Enable IP routing on the interface.

—End—

Refer to subsequent chapters in this document for detailed instructions on

conﬁguring IP routes.

Address Resolution Protocol (ARP)

Network stations using the IP protocol need both a physical address and an

IP address to transmit a packet. If a network station knows only a network

host’s IP address, the Address Resolution Protocol (ARP) enables the

network station to determine a network host’s physical address and bind

the 32-bit IP address to a 48-bit MAC address. A network station can use

ARP across a single network only, and the network hardware must support

physical broadcasts.

If a network station wants to send a packet to a host but knows only the

host’s IP address, the network station uses ARP to determine the host’s

physical address as follows:

1. The network station broadcasts a special packet, called an ARP request,

that asks the host at the speciﬁed IP address to respond with its physical

address.

2. All network hosts receive the broadcast message.

3. Only the speciﬁed host responds with its hardware address.

4. The network station then maps the host’s IP address to its physical

address and saves the results in an address resolution table for future

use.

5. The network station’s ARP table displays the association of the known

MAC addresses to IP addresses.

Note: The default timeout value for ARP entries is 6 hours.

Static ARP entries can be created and individual ARP entries deleted.

Nortel Ethernet Routing Switch 5500 Series

Conﬁguration-IP Routing Protocols

NN47200-503 03.01 Standard

5.1 27 August 2007