Nortel Networks NN47200-503 manual Configuring Ospf areas, Ospf network example

138IP Routing Configuration and Management

OSPF network example

To create the configuration illustrated above for router R1, use the following commands:

5530-24TFD(config)# vlan create 2 type port

5530-24TFD(config)# vlan mem add 2 1

5530-24TFD(config)# interface vlan 2

5530-24TFD(config-if)# ip address 172.3.1.1 255.255.255.0

5530-24TFD(config-if)# ip ospf network passive

The Nortel Ethernet Routing Switch 5500 Series supports the following types of networks:

•Broadcast - Automatically discovers every OSPF router on the network by sending OSPF hellos to the multicast group AllSPFRouters (224.0.0.5). Neighboring is automatic and requires no configuration. This interface type is typically used in an Ethernet environment.

•Passive - Allows interface network to be included in OSPF without generating LSAs or forming adjacencies. Typically used on an access network, or on an interface that is used for BGP peering. This also limits the amount of CPU cycles required to process the OSPF routing algorithm.

Configuring OSPF areas

In large networks with many routers and networks, the link state database (LSDB) and routing table can become very large. Large route tables and link state databases (LSDB) consume memory. The processing of link state advertisements results in more CPU cycles required to make forwarding decisions. To help reduce these undesired effects, an OSPF network can be divided into subdomains called areas. An area is made up of a number of OSPF routers that have the same area identification.

By dividing a network into multiple areas, a separate LSDB, consisting of router link state advertisements (LSA) and network LSAs are maintained for each area. Each router within an area maintains an LSDB only for the area to which it belongs. For example, the area router LSAs and network LSAs are not flooded beyond the area borders.

Nortel Ethernet Routing Switch 5500 Series

Configuration-IP Routing Protocols

NN47200-503 03.01 Standard

5.127 August 2007

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