Nortel Networks NN47200-503 manual Ospf router types, Ospf host route

IP routing 29

8.From this database each router calculates a shortest-path tree, with itself as root. This shortest-path tree in turn yields a routing table for the protocol.

OSPF router types

Routers in an OSPF network can take on different roles depending their configuration. The following table describes the router types in an OSPF network.

OSPF router types

Router Type	Description
Autonomous System	A router attached at the edge of an OSPF network
Boundary Router	is called an AS boundary router (ASBR). An ASBR
(ASBR)	generally has one or more interfaces that run an
	inter-domain routing protocol. In addition, any router
	distributing static routes or RIP routes into OSPF is
	considered an ASBR. The ASBR forwards external
	routes into the OSPF domain. In this way, routers inside
	the OSPF network learn about destinations outside their
	domain.
Area Border Router	A router attached to two or more areas inside an OSPF
(ABR)	network is considered an area border router (ABR). ABRs
	play an important role in OSPF networks by condensing
	the amount of OSPF information that is disseminated.
Internal Router (IR)	A router that has interfaces only within a single area
	inside an OSPF network is considered an internal router
	(IR). Unlike ABRs, IRs have topological information only
	about the area in which they are contained.
Designated Router	In a broadcast network a single router is elected to
(DR)	be the designated router (DR) for that network. A DR
	assumes the responsibility of making sure all routers on
	the network are synchronized with one another and also
	advertises that network to the rest of the AS.
Backup Designated	A backup designated router (BDR) is elected in addition
Router (BDR)	to the designated router (DR) and, in the event of failure
	of the DR, will assume its role quickly.

OSPF host route

An OSPF router with hosts directly attached to its interfaces can use host routes to advertise the attached hosts to its neighbors. You can configure up to 32 host routes.

Nortel Ethernet Routing Switch 5500 Series

Configuration-IP Routing Protocols

NN47200-503 03.01 Standard

5.127 August 2007

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