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Catalyst 3550 Multilayer Switch Software Configuration Guide
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Chapter22 Configuring IP Unicast Routing Configuring OSPF
Configuring OSPF
This section briefly describes how to configure Open Shortest Path First (OSPF). For a complete
description of the OSPF commands, refer to the “OSPF Commands” chapter of the Cisco IOS IP and IP
Routing Command Reference for Release 12.1.
Note OSPF classifies different media into broadcast, nonbroadcast, and point-to-point networks. The
Catalyst 3550 switch supports broadcast (Ethernet, Token Ring, and FDDI) and point-to-point
networks (Ethernet interfaces configured as point-to-point links).
OSPF is an Interior Gateway Protocol (IGP) designed expressly for IP networks, supporting IP
subnetting and tagging of externally derived routing information. OSPF also allows packet
authentication and uses IP multicast when sending and receiving packets. The Cisco implementation
supports RFC 1253, OSPF management information base (MIB).
For protocol-independent features that include OSPF, see the “Configuring Protocol-Inde pendent
Features” section on page 22-53.
The Cisco implementation conforms to the OSPF Version 2 specifications with these key features:
•Stub areas—Definition of stub areas is supported.
•Route redistribution—Routes learned through any IP routing protocol can be redistributed into
another IP routing protocol. At the intradomain level, this means that OSPF can import routes
learned through IGRP and RIP. OSPF routes can also be exported into IGRP and RIP.
•Authentication—Plain text and MD5 authentication among neighboring routers within an area is
supported.
•Routing interface parameter—Configurable parameters supported include interface output cost,
retransmission interval, interface transmit delay, router priority , router dead and hello intervals, and
authentication key.
•Virtual links—Virtual links are supported.
•Not-so-stubby-area (NSSA)—RFC 1587.
OSPF typically requires coordination among many internal routers, area border routers (ABRs)
connected to multiple areas, and autonomous system boundary routers (ASBRs). The minimum
configuration would use all default parameter values, no authentication, and inte rfaces assigned to areas.
If you customize your environment, you must ensure coordina te d con fi gura tion o f all r outers.
Table22-7 shows the default OSPF configuration .