Cisco Systems 3750E manual Controlling Advertising and Processing in Routing Updates, 38-88

Chapter 38 Configuring IP Unicast Routing

Configuring Protocol-Independent Features

	Command	Purpose
Step 7
	end	Return to privileged EXEC mode.
Step 8
	copy running-config startup-config	(Optional) Save your entries in the configuration file.

Use a network monitoring privileged EXEC command such as show ip ospf interface to verify the interfaces that you enabled as passive, or use the show ip interface privileged EXEC command to verify the interfaces that you enabled as active.

To re-enable the sending of routing updates, use the no passive-interfaceinterface-idrouter configuration command. The default keyword sets all interfaces as passive by default. You can then configure individual interfaces where you want adjacencies by using the no passive-interfacerouter configuration command. The default keyword is useful in Internet service provider and large enterprise networks where many of the distribution routers have more than 200 interfaces.

Controlling Advertising and Processing in Routing Updates

You can use the distribute-listrouter configuration command with access control lists to suppress routes from being advertised in routing updates and to prevent other routers from learning one or more routes. When used in OSPF, this feature applies to only external routes, and you cannot specify an interface name.

You can also use a distribute-listrouter configuration command to avoid processing certain routes listed in incoming updates. (This feature does not apply to OSPF.)

Beginning in privileged EXEC mode, follow these steps to control the advertising or processing of routing updates:

	Command	Purpose
Step 1
	configure terminal	Enter global configuration mode.
Step 2 router {bgp rip eigrp}		Enter router configuration mode.
Step 3
	distribute-list{access-list-number	Permit or deny routes from being advertised in routing
	access-list-name}out [interface-name routing	updates, depending upon the action listed in the access list.
	process autonomous-system-number]
Step 4
	distribute-list{access-list-number	Suppress processing in routes listed in updates.
	access-list-name}in [type-number]
Step 5
	end	Return to privileged EXEC mode.
Step 6
	copy running-config startup-config	(Optional) Save your entries in the configuration file.

Use the no distribute-list in router configuration command to change or cancel a filter. To cancel suppression of network advertisements in updates, use the no distribute-list out router configuration command.

Filtering Sources of Routing Information

Because some routing information might be more accurate than others, you can use filtering to prioritize information coming from different sources. An administrative distance is a rating of the trustworthiness of a routing information source, such as a router or group of routers. In a large network, some routing protocols can be more reliable than others. By specifying administrative distance values, you enable the

	Catalyst 3750-E and 3560-E Switch Software Configuration Guide
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