Intel 480T, User Manual

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C H A P T E R 1 1 RIP and OSPF
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• Multicasting
RIP version 2 packets can be multicast instead of being
broadcast, reducing the load on hosts that do not support routing
protocols.
If you are using RIP with supernetting/Classless Inter-Domain
Routing (CIDR), you must use RIPv2 only. In addition, RIP route
aggregation must be turned off.
Overview of OSPF
OSPF is a link-state protocol that distributes routing information
between routers belonging to a single IP domain, also known as an
autonomous system (AS). In a link-state routing protocol, each
router maintains a database describing the topology of the
autonomous system. Each participating router has an identical
database maintained from the perspective of that router.
From the link-state database (LSDB), each router constructs a tree
of shortest paths, using itself as the root. The shortest path tree
provides the route to each destination in the autonomous system.
When several equal-cost routes to a destination exist, traffic can be
distributed among them. The cost of a route is described by a single
metric.
Link-State Database
Upon initialization, each router transmits a link-state advertisement
(LSA) on each of its interfaces. LSAs are collected by each router
and entered into the LSDB of each router. OSPF uses flooding to
distribute LSAs between routers. Any change in routing
information is sent to all of the routers in the network. All routers
within an area have the exact same LSDB. Table 50 describes LSA
type numbers.