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| 8.3 |  | Route Redistribution |
| 8.3.6 |  | Configuring two-way redistribution |

The boundary router can be configured for two-way redistribution, as shown in Figures - .

Notice that the syntax of the metric keyword varies depending on the routing protocol that it uses. For RIP, OSPF, and BGP, the metric option is followed by a single number that represents the metric value (hop count, cost, and so on). For IGRP and EIGRP, the metric option is followed by five values that represent bandwidth, delay, reliability, load, and MTU.

> Note: Whenever there is a major network that is subnetted, use the keyword subnets to redistribute protocols into OSPF. Without this keyword, OSPF redistributes only major networks that are not subnetted. For example, to inject EIGRP routes, including subnets, into an OSPF area, use the command redistribute eigrp 24 metric 100 subnets.

In Figure , RIP is configured to import EIGRP routes and distribute them into the RIP domain with a seed metric of two hops.

Mutual redistribution will result in RTC installing 11 routes in its table (click on the topology Figure to view RTC routing table).

Unlike EIGRP, RIP does not differentiate between external and internal routes. Also, note that RTB seed metric has resulted in a metric of two hops for all the redistributed routes, even though two of these networks are actually three hops away.

After configuring two-way redistribution, RTC and RTA have only 11 routes, while the boundary router (RTB) has 12. What is happening? The answer lies in the directly connected routes of router RTB as follows:

- 172.16.0.0/16 (missing from RTA table)
- 172.24.0.0/16 (missing from RTC table)

Recall that the network command identifies not only which interfaces to run the routing protocol on, but also which directly connected networks will be included in routing updates. Look carefully in Figure . RTB RIP process is configured to advertise the connected network 172.16.0.0, while its EIGRP process is configured to advertise the connected network 172.24.0.0.

To bring RTA and RTC routing tables up to a complete 12 routes, we can configure both of RTB routing processes to include the two connected networks using the network command. However, that will result in a RIP process running in the EIGRP AS and an EIGRP process running in the RIP domain. This solution will generate needless overhead. Redistribution offers a much more efficient and elegant solution. RTB can be configured to redistribute its connected routes using a default metric, as discussed in the following sections.

| Lab Activity e-Lab Activity: Configuring Two-way Redistribution This lab is to configure RTB to accomplish a two-way redistribution of RIP and EIGRP routes.