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Introduction to Redistribution

March 13, 2024 , ,

Introduction to Redistribution

A routing protocol is a set of rules that routers use to communicate and share information with each other. This information helps them determine the best path to send data packets across a network to their final destination.

 What is Redistribution ?

Redistribution is the process of exchanging routing information across different routing protocols. It effectively allows routers to share network paths learned through one protocol with other protocols connected to the same router. 

Redistribution allows a router to take routes learned from one protocol and advertise them to other routing protocols running on the same router. This enables networks utilizing different protocols to share information with each other.

 Why we need Redistribution ?

Complex networks often divide into administrative domains, with each potentially using a different routing protocol according to its size, security requirements, or other reasons. Redistribution enables these domains to exchange routing information, allowing devices from one domain to communicate with devices from another.

When a large organization acquire other small organizations, their networks must be merged due to the reason as they may have used different routing protocols used in their network, redistribution overcomes the gap and ensures smooth communication throughout the recently brought together network.

 Where can we do Redistribution ?

Redistribution can be done

  • Between routing protocols (RIP, OSPF, EIGRP, BGP).
  • Static routes can be redistributed into a routing protocol.
  • Directly connected routes can be redistributed into a routing protocol.

 Redistribution Scenario

In our lab scenario, we are going to do redistribution between OSPF and EIGRP protocol. 

Redistribution OSPF to EIGRP
Fig 1.1- Redistribution OSPF to EIGRP

The main configuration is on Router R3 which is connected with OSPF and EIGRP protocols on two different interfaces.  Just concentrate on Router R3 configuration. Lets see how we are going to redistribute 

Redistribution between OSPF and EIGRP


Redistribute EIGRP in OSPF on Router R3

R3>enable
R3#configure terminal
R3(config)#router ospf 1
R3(config-router)#redistribute eigrp 20 metric 50000 subnets
R3(config-router)#exit
R3#
Now lets Redistribute OSPF in EIGRP on Router R3

R3>enable
R3#configure terminal
R3(config)#router eigrp 20
R3(config-router)#redistribute ospf 1 metric ?
  <1-4294967295>  Bandwidth metric in Kbits per second

R3(config-router)#redistribute ospf 1 metric 1544 ?
  <0-4294967295>  EIGRP delay metric, in 10 microsecond units

R3(config-router)#redistribute ospf 1 metric 1544 2000 ?
  <0-255>  EIGRP reliability metric where 255 is 100% reliable

R3(config-router)#redistribute ospf 1 metric 1544 2000 255 ?
  <1-255>  EIGRP Effective bandwidth metric (Loading) where 255
is 100% loaded

R3(config-router)#redistribute ospf 1 metric 1544 2000 255 1 ?
  <1-65535>  EIGRP MTU of the path 

R3(config-router)#redistribute ospf 1 metric 1544 2000 255 1 1500
R3(config-router)#end
R3#
Hope this example helps to understand the redistribution between OSPF and EIGRP on Router R3. We will take another example in another article to have redistribution between OSPF and BGP or EIGRP and BGP.