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The nature of DDR networks is that
routing and some directory services tables must be maintained over
idle connections. DDR designers may use a combination of static,
dynamic, and snapshot routing techniques to meet design needs.
Default routing and remote node spoofing techniques (such as Cisco
IOS EZIP) can be used to greatly simplify routing design.
Often the backbone at the NAS
(network access server) site
will use a fast-converging routing protocol such as OSPF or EIGRP;
however, these protocols do not operate easily on the dialer media
due to their broadcast and link-state nature. Typically, static
routing and/or distance vector routing protocols are selected for
the DDR connections. Routing redistribution may be required to
support propagation of routing information between the different
routing protocols.
A complete discussion of routing
redistribution techniques is beyond the scope of this chapter;
however, DDR designers do need to develop and verify their routing
strategy for each network protocol.
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