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It is sometimes necessary to accommodate
more complex network topologies such as independent RIP and OSPF
clouds that must perform mutual redistribution. In this scenario, it
is critically important to prevent potential routing loops by
filtering routes. The router in the main figure is running both OSPF and
RIP.
With the following commands, OSPF routes will be redistributed
into RIP. You must specify the default metric to designate the cost
of the redistributed route in RIP updates. All routes redistributed
into RIP will have this default metric. (see
Router#show running-config
(1) command output).
It is a good practice to strictly control which routes are
advertised when redistribution is configured. In the following
example, a distribute-list out command causes RIP to ignore routes
coming from the OSPF that originated from the RIP domain. (see
Router#show running-config
(2) command output).
Because it is common for OSPF and RIP to
be used together, it is important to use the practices described
here in order to provide functionality for both protocols on an
internetwork. You can configure ASBRs that run both RIP and OSPF and
redistribute RIP routes into the OSPF and vice versa. You can also
create OSPF areas using ABRs that provide route summarizations. Use
VLSM to conserve address space.
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