EIGRPv4

  • Eigrp should be configured with same eigrp process number on the neighboring routers otherwise there will be no neighborship.
  • If no wild-card mask is configured on the eigrp network command, the command's single parameter should be classful network number. If wild-card mask is configured, it performs like ACL logic.

Hellos are multicast every 5 seconds, minus a small random time to prevent synchronization.
On multipoint X.25, Frame Relay, and ATM interfaces, with access link speeds of T1 or slower, Hellos are unicast every 60 seconds.

The hold time tells the router the maximum time it should wait to receive subsequent Hellos. If the hold timer expires before a Hello is received, the neighbor is declared unreachable and DUAL is informed of the loss of a neighbor. By default, the hold time is three times the Hello interval—180 seconds for low-speed non-broadcast multi-access (NBMA) networks and 15 seconds for all other networks. The default can be changed on a per interface basis with the command ip hold-time eigrp.
Full updates occur when neighbors first come up. After that, the neighbors send only partial updates in reaction to changes to a route.

Reliable Transport Protocol

In this formula, the term least-bandwidth represents the lowest-bandwidth link in the route, using a unit of kilobits per second

 

EIGRP hello and hold timer configurations :


these settings are made on interfaces only not per neighbor. where 9 is asn

Passive interface

router eigrp 1
passive-interface default

Two commands help to verify that the passive interface design is working properly.
First, the show ip eigrp interfaces command omits passive interfaces, listing the non-passive interfaces matched by a network command. Alternatively, the show ip protocols command explicitly lists all passive interfaces.


EIGRP Authentication

Step1
  • Create a chain and give it a name 
     router(config)#key chain cisco
     router(config-keychain)#

the name does not need to match on neighboring routers.
  •  Create one or more key number using the key number command in key configuration mode.
     router(config)#key chain cisco
     router(config-keychain)#key 1
     router(config-keychain-key)#                     (key number should be same)

define key's value using key-string value command in key configuration mode.
router(config-keychain-key)#key-string book

step2. Enable Eigrp MD5 authentiocation on an interface
config)#int f0/0
config-if)#ip authentication mode eigrp asn md5
config-if)#ip authentiation key-chain eigrp asn name of the chain




Important :-

# to check the delay, bandwidth MTU, etc
show interfaces

# to check the K-values
Show ip protocols











Commands for EIGRPv4

sh ip protocols
sh ip eigrp interfaces
sh ip eigrp neighbors
sh ip eigrp topology
sh ip route

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