ExtremeWare XOS 11.3 Concepts Guide
543
27 OSPF
This chapter covers the following topics:
● Overview of OSPF on page 543
● Route Redistribution on page 550
● Configuring OSPF on page 551
● OSPF Configuration Example on page 553
● Displaying OSPF Settings on page 555
This chapter assumes that you are already familiar with IP unicast routing. If not, refer to the following
publications for additional information:
● RFC 2328—OSPF Version 2
● RFC 1765—OSPF Database Overflow
● RFC 2370—The OSPF Opaque LSA Option
● RFC 3101—The OSPF Not-So-Stubby Area (NSSA) Option
● RFC 3623—Graceful OSPF Restart
● Interconnections: Bridges and Routers
by Radia Perlman
ISBN 0-201-56332-0
Published by Addison-Wesley Publishing Company
Overview of OSPF
Open Shortest Path First (OSPF) is a link state protocol that distributes routing information between
routers belonging to a single IP domain; the IP domain is also known as an autonomous system (AS). In a
link-state routing protocol, each router maintains a database describing the topology of the AS. 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 AS. 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.
OSPF is an interior gateway protocol (IGP), as is the other common IGP, RIP. OSPF and are compared in
Chapter 25, “RIP” on page 531.
Licensing
To use the complete OSPF functionality, you must have a Core license installed on your switch. The
BlackDiamond 10K ships with a Core, or Advanced Core license. Other platforms can be upgraded to a
Core license. See the section “Software Licensing” on page 33 for more information about licensing.
A subset of OSPF, called OSPF Edge Mode, is available with an Advanced Edge license.
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