Why redistribution works

Router1 config router eigrp Router1 config-router network Router3 config ip route Now, redistribution on Router2 Router2 config router Eigrp Router2 config-router redistribute static metric 1 0 1 1 1 Note — There is no need to give static route on Router2 as it is directly connected to Configuring default route on Router1. Router1 config ip route 0. Skip to content. Change Language.

Related Articles. Table of Contents. Save Article. You probably wrote it in the lesson, but I had to complete:. The How the routers can distinguish between one network or another? This single router is running 2 protocols thus redistribution is done on it. What if Router 1 was running RIP only. Router 1 is connected to Router 2. Is that possible? Ask a question or join the discussion by visiting our Community Forum. Skip to content Search for: Search.

Routers are configured in several ways that enable them to learn a route. The simplest method is to manually configure static routes. A static route tells the router exactly where to send packets. For example, a static route tells Router 1 to route packets to Router 2, and then Router 2 is manually configured to send packets to Router 3.

The issue with static routes is that many routes change configurations — and the patch from one router to another often changes as a network grows. You can have thousands of different routes, and if one changes, you could be left manually configuring several routers.

This can be a time-consuming process, especially when it comes to larger networks. A better option is to allow routers to share configurations with neighboring routers. This enables them to dynamically learn the right path for their packets. For instance, if Router 1 is connected to Router 2 and Router 4, it would share its path with both of them. The RIP metric is composed of hop count, and the maximum valid metric is Anything above 15 is considered infinite; you can use 16 to describe an infinite metric in RIP.

When redistributing a protocol into RIP, Cisco recommends that you use a low metric, such as 1. A high metric, such as 10, limits RIP even further. If you define a metric of 10 for redistributed routes, these routes can only be advertised to routers up to 5 hops away, at which point the metric hop count exceeds By defining a metric of 1, you enable a route to travel the maximum number of hops in a RIP domain. But, doing this increases the possibility of routing loops if there are multiple redistribution points and a router learns about the network with a better metric from the redistribution point than from the original source, as explained in the Administrative Distance section of this document.

Therefore, you have to make sure that the metric is neither too high, preventing it from being advertised to all the routers, or too low, leading to routing loops when there are multiple redistribution points. This configuration is an example of redistributing static routes except gateway of last gateway resort in RIP through routemap. Redistribute in RIP using route-map at and remove the default information originate command from the rip process.

The IS-IS metric must be between 1 and There is no default-metric option in IS-IS—you should define a metric for each protocol, as shown in the example above. If no metric is specified for the routes being redistributed into IS-IS, a metric value of 0 is used by default. Redistributing directly connected networks into routing protocols is not a common practice and is not shown in any of the examples above for this reason.

However, it is important to note that it can be done, both directly and indirectly. In order to directly redistribute connected routes, use the redistribute connected router configuration command. You should also define a metric in this case. You can also indirectly redistribute connected routes into routing protocols as shown in this example.

In this example, Router B has two Fast Ethernet interfaces. This is the pertinent configuration information for Router B:. Network Router A has learned about network Router C has learned about network Although Router B is not redistributing connected networks, it does advertise the network Similarly, Router B advertises network In the section on administrative distance you saw how redistribution can potentially cause problems such as below optimal routing, routing loops, or slow convergence.

Avoiding these types of problems is really quite simple—never announce the information originally received from routing process X back into routing process X.