Introduction to RIP and EIGRP

 Why is RIPv1 largely absent from today's networks? This original version of the Routing information Protocol has limitations that weren't bad when it was originally developed, but those same limitations prohibit their use today. 

  1. RIPv1 sends a full routing update at a fixed interval.
  2. RIPv1 doesn't understand subnet mask. 
Split Horizon: The rule of split horizon is simple. A route can't be advertised via an interface if that same interface is the one that learned about the route in the first place. 

Route Poisoning: When router agree on the current state of the network, they have reached a stat of convergence. A major reason you don't see a lot of distance-vector routing out there is that DV protocols are very slow to converge, even in a lab environment. 

RIP in action: 

R1(config)router rip
R1(config-router)#network 172.12.0.0 
R1(config-router)#^Z
R1#show IP protocols
Aromatic network summarization is in effect

R1#conf t
R1(config)#router rip
R1(config-router)#version 2
R1(config-router)#no auto-summary
R1(config-router)#no auto
R1(config-router)#^Z

R2#conf t
R2(config)#router rip
R2(config-router)#version 2
R2(config-router)#no auto
R2(config-router)#network 172.12.0.0 
R2(config-router)#network 2.0.0.0
R2(config-router)#^Z
R2#wr

R3#conf t
R3(config)#router rip
R3(config-router)#version 2
R3(config-router)#no auto
R3(config-router)#network 172.12.0.0 
R3(config-router)#network 3.0.0.0
R3(config-router)#^Z
R3#wr

R1#show ip route rip
R1#ping 2.2.2.2

R1#
R1#conf t
R1(config)#int serial 0/3/0
R1(config-if)#no ip split-horizon
R1(config-router)#^Z
R1#clear rip route *


EIGRP Fundamentals
Over the years, EIGRP has been called a hybrid protocol, since it officially has characteristics of link-state and distance-vector protocols. EIGRP acts much more like an LS protocol than a DV protocol. The main DV behavior shown by EIGRP is the initial exchange of full routing tables between EIGRP neighbors. 

EIGRP Advantages:

  • Rapid convergence. Backup paths ("feasible successors are calculated in advance of actually being needed. 
  • Full subnet mask support
  • Takes bandwidth into account when calculating routes (no "hop count").
  • No longer cisco-proprietary
EIGRP in action:

R1#conf t
R1(config)#router eigrp 100
R1(config-router)#no auto
R1(config-router)#network 172.12.123.0 0.0.0.255

R2#conf t
R2(config)#router eigrp 100
R2(config-router)#no auto
R2(config-router)#network 172.12.123.0 0.0.0.255

R3#conf t
R3(config)#router eigrp 100
R3(config-router)#no auto
R3(config-router)#network 172.12.123.0 0.0.0.255

R1#show ip eigrp neighbor

Administrative Distance:

Connected

0

Static

1

EIGRP Summary

5

EIGRP Internal

90

OSPF

110

IS-IS

115

RIP (both versions)

120

EIGRP External

170

BGP Internal /Ext.

200 / 20

Unknown (Untrusted)

255



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