Explore the fundamentals as well as prerequisites required for redistribution between interior gateway routing protocols (IGP) in Cisco networks. Learn about the redistribute command.
- [Instructor] The need for route redistribution exists in most networks. Redistribution is simply taking routes from any source external to a routing protocol and then injecting them in. Say for example I have static routes I want to introduce into OSPF. I'll use redistribution to inject them. Redistribution is also used when transitioning from one dynamic routing protocol to another or during network mergers. On a router that will perform redistribution, three things need to be in place, a working interface in each routing domain, the routing protocol to be functioning in each of these domains, and a redistribute command properly configured for the desired routing protocol.
At each routing protocol's core, they maintain the topology table. Each protocol maintains a different set of information in their respective table and each protocol operates quite differently inside. Keeping this in mind, when redistribution is configured, a protocol won't pull directly from another protocol's topology table and instead it will look at the local routing table for any routes created by the alternate protocol. The redistribution command will also give an administrator the ability to manipulate metrics for routes being introduced into the protocol.
This is the router EIGRP sub command used when redistributing routes in the EIGRP. The amount of options can be quite daunting. The protocol in the command is the routing information source RIP, OSPF, EIGRP, ISIS, BGP, static, and connected. If the protocol being redistributed uses an ASN or process ID, it needs to be specified. The metric keyword is then followed by the EIGRP core components metric bandwidth, delay, reliability, load, and last MTU.
The match keyword allows OSPF redistributed routes to be matched for specific type like internal or NSSA. The tag keyword will assign a standard route tag that can later be matched in route maps. The route map keyword allows redistribution to be run through a route map for more fine grain matching and filtering. Redistribution has been used in every network I've ever configured and it's likely to be the same for you.
- Enhanced Interior Gateway Routing Protocol (EIGRP) configuration
- Common ways to prevent suboptimal routing and routing loops
- Performing packet switching
- Using policy-based routing (PBR) in a modern network
- Implementing policy-based routing (PBR) to modify routing for specific clients or services
- Using Cisco IP Service Level Agreement (IP SLA) to test and react to network conditions