Cisco Systems 3750E manual Using Route Maps to Redistribute Routing Information, 38-80

Chapter 38 Configuring IP Unicast Routing

Configuring Protocol-Independent Features

	Command	Purpose
Step 3
	end	Return to privileged EXEC mode.
Step 4
	show ip route	Display the selected default route in the gateway of last resort
		display.
Step 5
	copy running-config startup-config	(Optional) Save your entries in the configuration file.

Use the no ip default-networknetwork number global configuration command to remove the route.

When default information is passed through a dynamic routing protocol, no further configuration is required. The system periodically scans its routing table to choose the optimal default network as its default route. In IGRP networks, there might be several candidate networks for the system default. Cisco routers use administrative distance and metric information to set the default route or the gateway of last resort.

If dynamic default information is not being passed to the system, candidates for the default route are specified with the ip default-networkglobal configuration command. If this network appears in the routing table from any source, it is flagged as a possible choice for the default route. If the router has no interface on the default network, but does have a path to it, the network is considered as a possible candidate, and the gateway to the best default path becomes the gateway of last resort.

Using Route Maps to Redistribute Routing Information

The switch can run multiple routing protocols simultaneously, and it can redistribute information from one routing protocol to another. Redistributing information from one routing protocol to another applies to all supported IP-based routing protocols.

You can also conditionally control the redistribution of routes between routing domains by defining enhanced packet filters or route maps between the two domains. The match and set route-map configuration commands define the condition portion of a route map. The match command specifies that a criterion must be matched. The set command specifies an action to be taken if the routing update meets the conditions defined by the match command. Although redistribution is a protocol-independent feature, some of the match and set route-map configuration commands are specific to a particular protocol.

One or more match commands and one or more set commands follow a route-mapcommand. If there are no match commands, everything matches. If there are no set commands, nothing is done, other than the match. Therefore, you need at least one match or set command.

You can also identify route-map statements as permit or deny. If the statement is marked as a deny, the packets meeting the match criteria are sent back through the normal forwarding channels (destination-based routing). If the statement is marked as permit, set clauses are applied to packets meeting the match criteria. Packets that do not meet the match criteria are forwarded through the normal routing channel.

You can use the BGP route map continue clause to execute additional entries in a route map after an entry is executed with successful match and set clauses. You can use the continue clause to configure and organize more modular policy definitions so that specific policy configurations need not be repeated within the same route map. Beginning in Cisco IOS Release 12.2(37)SE, the switch supports the continue clause for outbound policies. For more information about using the route map continue clause, see the BGP Route-Map Continue Support for an Outbound Policy feature guide for Cisco IOS Release 12.4(4)T at this URL:

http://www.cisco.com/en/US/products/ps6441/products_feature_guides_list.html

	Catalyst 3750-E and 3560-E Switch Software Configuration Guide
38-80	OL-9775-02