INTERNETWORK EXPERT .ORG 

** EIGRP NOTES **

IP Protocol 88

Updates and Neighbor discovery on 224.0.0.10

EIGRP require acknowledgements from routing updates.

Updates sent to 224.0.0.10 - unicast ACKs are expected.

Each update message is given a sequence number, and the recieved ACK should have the same sequence number.

‘delay’ values configured per interface in EIGRP are in tens of microseconds.

‘bandwidth’ values are in kilobits per second.

delay 100 = 1000 usecs or 1 milisecond

bandwidth 10000 = 10,000,000 bits per second or 10Mbits/sec.

default metric = 256 * (10,000,000/bw) + 256 * (delay)

K1 value is BW

K3 value is Delay

‘metric wieghts 0  1  0  1  0  0′

                   K1 K2 K3 K4 K5

feasibility condition:

The RD must be lower then the current best FD for the route

when a route goes “stuck in active” the router takes down any neighbors who did not respond to the Queries within the Active timer.

The Active timer can be disabled with ‘timers active-time disabled’.

EIGRP hello time defaults to 5 seconds on most interfaces.

on NBMA interfaces with T1 or less BW the hello time is 60 seconds.

EIGRP only allows FS routes to be evaluated with the ‘variance’ command

‘ip summary-address eigrp 1 0.0.0.0 0.0.0.0′ can be used to source a default route in EIGRP, however care must be taken that the Null0 route created for the summary does not override any other default route.

If an eBGP default route exists in the routing table, you can set the EIGRP Null0 summary admin distance to something higher than 20, to prevent it from overriding the BGP default route.