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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.
In Figure
Mutual redistribution will result in RTC
installing 11 routes in its table (click on the topology Figure
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:
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
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.
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