EIGRP Authentication and some EIGRP "tuning" options

EIGRP Authentication

Like in OSPF - the configuration is done in the Interface Configuration mode. Unlike OSPF - EIGRP supports only MD5 authentication. Set the mode to MD5, even though it's the default mode on most devices.

This is an example of Frame relay P2P Interface and EIGRP authentication

interface Serial4/1.25 point-to-point
 ip address 134.12.122.2 255.255.255.0
 ip authentication mode eigrp 100 md5
 ip authentication key-chain eigrp 100 EIGRP_CHAIN
 frame-relay interface-dlci 201   
end


EIGRP: Maximum Hops

Another attribut that can be useful for controlling the routes is the "maximum-hops". To see each routes hop count:

#show ip route 172.28.185.0
  Known via "eigrp 100", distance 90, metric 2297856, type internal
  Redistributing via eigrp 100
  Last update from 131.1.12.2 on Serial1/0.12, 00:13:47 ago
  Routing Descriptor Blocks:
  * 131.1.12.2, from 131.1.12.2, 00:13:47 ago, via Serial1/0.12
      Route metric is 2297856, traffic share count is 1
      Total delay is 25000 microseconds, minimum bandwidth is 1544 Kbit
      Reliability 255/255, minimum MTU 1500 bytes
      Loading 1/255, Hops 12 <-- 12 HOPS TO THIS ROUTE!!!

To change the Maximum number of Hops to, for example, 10 (Its 100 by Default):

Cisqueros_1(config-router)#metric maximum-hops 10


EIGRP Administrative Distance

By default EIGRP has the following Administrative Distance values:
170 - External EIGRP Routes
90 - Internal EIGRP Routes
5 - EIGRP Summary Routes

You can make EIGRP External routes smaller if you need them to not be less prefered then, for example, OSPF, that has AD 110 for External routes:

Cisqueros_1(config-router)#distance eigrp 90 100