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Cisco ME 3400 EthernetAccess Switch SoftwareConfiguration Guide
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Chapter32 Configuring IP Unicast Routing Steps for Configuring Routing
•Routers using link-state protocols maintain a complex database of network top ology, based on the
exchange of link-state advertisements (LSAs) between routers. LSAs are triggered by an event in
the network, which speeds up the convergence time or time required to respond to these changes.
Link-state protocols respond quickly to topology changes, but require greater bandwidth a nd m ore
resources than distance-vector protocols.
Distance-vector protocols supported by the switch are Routing Information Protocol (RIP), which use s
a single distance metric (cost) to determine the best path and Border Gateway Protocol (BGP), which
adds a path vector mechanism. The switch also supports the Open Shortest Path First (OSPF) link-state
protocol and Enhanced IGRP (EIGRP), which adds some link-stat e r outi ng fe a tures to tra dit ional
Interior Gateway Routing Protocol (IGRP) to improve efficiency.
Steps for Configuring Routing
By default, IPv4 routing is disabled on the switch, and you must enable it before routing ca n take place.
For detailed IP routing configuration information, see the Cisco IOS IP Configuration Guide,
Release12.2
In the following procedures, the specified interface must be one of these Layer 3 interfaces:
•A routed port: a physical port configured as a Layer 3 port by using the no switchport interface
configuration command.
•A switch virtual interface (SVI): a VLAN interface created by using the interface vlan vlan_id
global configuration command and by default a Layer 3 interface.
•An EtherChannel port channel in Layer 3 mode: a port-c hann el lo gica l i n terfa ce c rea ted by usi ng
the interface port-channel port-channel-number global configuration command and binding the
Ethernet interface into the channel group. For more information, see the “Configuring Layer 3
EtherChannels” section on page 31-13.
Note The switch does not support tunnel interfaces for unicast routed traffic.
All Layer 3 interfaces on which routing will occur must have IP addresses assigned to them. See the
“Assigning IP Addresses to Network Interfaces” section on page 32-5.
Note A Layer 3 switch can have an IP address assigned to each routed port and SVI. The number of routed
ports and SVIs that you can configure is not limited by software. However, the interrelationship between
this number and the number and volume of features being implemented might have an impact on CPU
utilization because of hardware limitations. To support routing, use the sdm prefer default global
configuration command.
Configuring routing consists of several main procedures:
•To support VLAN interfaces, create and configure VLANs on the switch, and assign VLAN
membership to Layer 2 interfaces. For more information, see Chapter11, “Configu ring VLAN s.”
•Configure Layer 3 interfaces.
•Enable IPv4 routing on the switch.
•Assign IPv4 addresses to the Layer 3 interfaces.
•Enable selected routing protocols on the switch.
•Configure routing protocol parameters (optional).