Route redistribution in is a process of exchanging routing information between different routing protocols, allowing routers running different protocols to share routes and make routing decisions based on the entire network topology. This tutorial will guide you through the basics of route redistribution in Cisco routers.

Understanding Route Redistribution

Route redistribution is necessary when multiple routing protocols are running within a network. It allows routes learned by one routing protocol to be advertised into another routing protocol, enabling routers running different protocols to communicate with each other.

Preparing for Route Redistribution

Before configuring route redistribution, it’s important to understand the routing protocols involved and plan the redistribution strategy. Identify which routing protocols will participate in redistribution and determine the routes to be redistributed.

Troubleshooting

If issues arise after configuring route redistribution, use these troubleshooting steps:

• Check Configuration: Review the configuration to ensure correctness, especially regarding metric values and ACLs.
• Verify Routing Updates: Use debug commands to monitor routing updates and identify any issues with redistribution.

Best Practices:

• Plan Carefully: Design a redistribution strategy based on network requirements and consider potential routing loops or suboptimal paths.
• Filter Routes: Use ACLs to control which routes are redistributed to prevent routing loops and minimize unnecessary traffic.
• Monitor and Test: Regularly monitor the network and test routing changes in a controlled environment before deploying them in production.

Sample Config (Cisco)

! Enable OSPF routing protocol
Router(config)# router ospf 1
Router(config-router)# network 192.168.1.0 0.0.0.255 area 0
Router(config-router)# exit

! Enable EIGRP routing protocol
Router(config)# router eigrp 100
Router(config-router)# network 10.0.0.0
Router(config-router)# exit

! Configure route redistribution from OSPF to EIGRP
Router(config)# router eigrp 100
Router(config-router)# redistribute ospf 1 metric 1000 100 255 1 1500
Router(config-router)# exit

! Configure route redistribution from EIGRP to OSPF
Router(config)# router ospf 1
Router(config-router)# redistribute eigrp 100 subnets
Router(config-router)# exit

! Apply ACL to filter redistributed routes (optional)
Router(config)# access-list 1 permit 192.168.2.0 0.0.0.255
Router(config)# router eigrp 100
Router(config-router)# distribute-list 1 out
Router(config-router)# exit

In this sample configuration:

• OSPF process ID is 1 and EIGRP AS number is 100.
• We redistribute OSPF routes into EIGRP with a metric of 1000, bandwidth 100, delay 255, reliability 1, and MTU 1500.
• EIGRP routes are redistributed into OSPF with the “subnets” keyword.
• An ACL (access-list 1) is applied to EIGRP to filter routes redistributed into OSPF, allowing only routes with destinations in the 192.168.2.0/24 network.

Remember to replace the network addresses, OSPF area, EIGRP AS number, and ACL entries with your specific network configurations. Additionally, ensure that the redistribution strategy aligns with your network requirements and routing policies.