Cisco Systems 78-11741-02 manual Configuring Eigrp Route Authentication, IPC-265

Configuring EIGRP

EIGRP Configuration Task List

Figure 47 Floating Summary Route Applied for Dual-Homed Remotes

	10.1.1.0/24
0.0.0.0/0	0.0.0.0/0
			Router-C
Router-A	Router-B
		0.0.0.0/0
Router-D	Router-E

0.0.0.0/0

103614

interface Serial 0/1

ip summary-address eigrp 100 0.0.0.0.0.0.0.0 250

Router-B#show ip route

. . . .

0.0.0.0.0.0.0.0via <Router-A> (489765/170)

However, if the link between Router-D and Router-E fails, the network may blackhole traffic because Router-E will continue to advertise the default route(0.0.0.0/0) to Router-C, as long as at least one link, (other than the link to Router-C) to Router-E is still active. In this scenario, Router-C still forwards traffic to Router-E, but Router-E drops the traffic creating the black hole. To avoid this problem, you should configure the summary address with an administrative distance on only single-homed remote routers or areas where there is only one exit point between to segments of the network. If two or more exit points exist (from one segment of the network to another), configuring the floating default route can cause a black hole to be formed.

Configuring EIGRP Route Authentication

EIGRP route authentication provides Message Digest 5 (MD5) authentication of routing updates from the EIGRP routing protocol. The MD5 keyed digest in each EIGRP packet prevents the introduction of unauthorized or false routing messages from unapproved sources.

Before you can enable EIGRP route authentication, you must enable EIGRP.

To enable authentication of EIGRP packets, use the following commands beginning in interface configuration mode:

	Command	Purpose
Step 1
	Router(config)# interface type number	Configure an interface type and enter interface
		configuration mode
Step 2
	Router(config-if)#ip authentication mode eigrp	Enables MD5 authentication in EIGRP packets.
	autonomous-system md5

Cisco IOS IP Configuration Guide

IPC-265