Setting Up IP Routing on the Switch
Page 25-4

Setting Up IP Routing on the Switch

IP routing is enabled on a per-port basis by creating a virtual IP router port for a group/VLAN.
The switch does not do any routing unless the virtual router port has IP routing enabled
(routing is enabled by default). The steps for setting up IP routing on the switch are given
here:

Step 1. Configuring a Virtual Router Port

A virtual router port may be created when you set up or modify a group/VLAN through the
crgp command or modvl command described in Chapter 19, “Managing Groups and Virtual
Ports.” To create a virtual router port, enable IP routing and specify an IP address for the
router port.
When routing is enabled on the port, the switch creates routing tables and address transla-
tion tables so it knows how to forward traffic. The switch keeps track of router ports and any
other routers in the network. The switch uses the Address Resolution Protocol (ARP) to match
IP addresses with MAC addresses. It uses routing protocols, such as the Routing Information
Protocol (RIP), to determine the best path for forwarding traffic. (Other routing protocols are
available in the Advanced Routing software package.) It also periodically sends/receives rout-
ing messages to/from other routers to keep its routing tables updated.
♦ Important Note ♦
When Spanning Tree and IP routing are both enabled,
packets are not forwarded unless the Spanning Tree
Status for the port to which packets are to be
forwarded has progressed from Listening to Learning to
Forwarding. For example, if IP is enabled on VLAN 42
that has ports 1/1-3 attached to it and you want to
forward to a host from port 1/2. Use the vi 1/2
command to determine if the Spanning Tree Protocol
has entered the Forwarding state for that port.

Step 2. Configuring Optional IP Routing Parameters

Optional configuration for IP routing includes the following:
• Static routes. These are routes that are manually added to the routing table and may be
used rather than dynamic routes (which are learned through routing protocols like RIP).
•RIP filters. Controls the operation of RIP by minimizing the number of entries that will be
added to the routing table.
Static routes and RIP filters are described in this chapter. This chapter also describes how to
view various IP statistics as well as the routing table. It includes information about how to
ping another IP host in the network, how to telnet to a remote system, and how to trace an IP
route.