Cisco Systems 3750E Managing Authentication Keys, Distance weight ip-address ip-address mask

Chapter 38 Configuring IP Unicast Routing

Configuring Protocol-Independent Features

router to intelligently discriminate between sources of routing information. The router always picks the route whose routing protocol has the lowest administrative distance. Table 38-14 on page 38-79shows the default administrative distances for various routing information sources.

Because each network has its own requirements, there are no general guidelines for assigning administrative distances.

Beginning in privileged EXEC mode, follow these steps to filter sources of routing information:

	Command	Purpose
Step 1
	configure terminal	Enter global configuration mode.
Step 2
	router {bgp rip ospf eigrp}	Enter router configuration mode.
Step 3
	distance weight {ip-address {ip-address mask}}	Define an administrative distance.
	[ip access list]	weight—The administrative distance as an integer from
		10 to 255. Used alone, weight specifies a default
		administrative distance that is used when no other
		specification exists for a routing information source.
		Routes with a distance of 255 are not installed in the
		routing table.
		(Optional) ip access list—An IP standard or extended
		access list to be applied to incoming routing updates.
Step 4
	end	Return to privileged EXEC mode.
Step 5
	show ip protocols	Display the default administrative distance for a
		specified routing process.
Step 6
	copy running-config startup-config	(Optional) Save your entries in the configuration file.

To remove a distance definition, use the no distance router configuration command.

Managing Authentication Keys

Key management is a method of controlling authentication keys used by routing protocols. Not all protocols can use key management. Authentication keys are available for EIGRP and RIP Version 2.

Before you manage authentication keys, you must enable authentication. See the appropriate protocol section to see how to enable authentication for that protocol. To manage authentication keys, define a key chain, identify the keys that belong to the key chain, and specify how long each key is valid. Each key has its own key identifier (specified with the key number key chain configuration command), which is stored locally. The combination of the key identifier and the interface associated with the message uniquely identifies the authentication algorithm and Message Digest 5 (MD5) authentication key in use.

You can configure multiple keys with life times. Only one authentication packet is sent, regardless of how many valid keys exist. The software examines the key numbers in order from lowest to highest, and uses the first valid key it encounters. The lifetimes allow for overlap during key changes. Note that the router must know these lifetimes.

	Catalyst 3750-E and 3560-E Switch Software Configuration Guide
OL-9775-02		38-89