Avaya Configuring IP, ARP, RARP, RIP, and OSPF Services Instrukcja Użytkownika Pobierz pdf (Strona 36)

Configuring IP, ARP, RARP, RIP, and OSPF Services

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Routing Information Protocol (RIP)

The Routing Information Protocol (RIP) is a distance-vector protocol that enables

routers in the same autonomous system to exchange routing information by means

of periodic RIP updates. Routers transmit their own RIP updates to neighboring

networks and listen for RIP updates from the routers on those neighboring

networks. Routers use the information in the RIP updates to keep their internal

routing tables current. For RIP, the “best” path to a destination is the shortest path

(the path with the fewest hops). RIP computes distance as a metric, usually the

number of hops (or routers) from the source network to the target network.

Open Shortest Path First (OSPF) Protocol

The Open Shortest Path First (OSPF) protocol is an interior gateway protocol

(IGP) intended for use in large networks. Using a link state algorithm, OSPF

exchanges topology information between routers in an autonomous system.

Routers synchronize their topological databases. After the routers are

synchronized and the routing tables are built, the routers flood topology

information only in response to some topological change. For OSPF, the “best”

path to a destination is the path that offers the least cost metric. In OSPF, cost

metrics are configurable, allowing you to specify preferred paths.

OSPF is a link state protocol. When the state of the interface to each of the

neighboring routers changes, a router running a link state protocol tests the status

of the physical connection and sends this information to the other neighbors. A

link state protocol does not require each router to send its entire routing table to its

neighbors. Instead, each OSPF router floods only link state change information

throughout the autonomous system (or area, if the AS is divided into areas). This

process is referred to as the synchronization of the routers’ topological databases.

With the link state information, each router builds a shortest-path tree with itself

as the root of the tree. It can then identify the shortest path from itself to each

destination and build its routing table.

OSPF supports CIDR and can carry supernet advertisements within a routing

domain.

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Avaya Configuring IP, ARP, RARP, RIP, and OSPF Services Instrukcja Użytkownika Strona 36