Configuring Ospf; Overview Of Ospf - Foundry Networks Switch and Router Installation And Configuration Manual

This chapter describes how to configure OSPF on Foundry Layer 3 Switches using the CLI and Web management
interface.
To display OSPF configuration information and statistics, see "Displaying OSPF Information" on page 17-41.
For complete syntax information for the CLI commands shown in this chapter, see the Foundry Switch and Router
Command Line Interface Reference.
NOTE: The TurboIron/8, Stackable NetIron, and Chassis Layer 3 Switches using basic management modules
(not Management II or higher) can contain 10000 routes by default. If you need to increase the capacity of the IP
route table, see "Displaying and Modifying System Parameter Default Settings" on page 10-70.

Overview of OSPF

OSPF is a link-state routing protocol. The protocol uses link-state advertisements (LSA) to update neighboring
routers regarding its interfaces and information on those interfaces. The router floods these LSAs to all
neighboring routers to update them regarding the interfaces. Each router maintains an identical database that
describes its area topology to help a router determine the shortest path between it and any neighboring router.
Foundry Layer 3 Switches support the following types of LSAs, which are described in RFC 1583:
• Router link
• Network link
• Summary link
• Autonomous system (AS) summary link
• AS external link
• NSSA external link
OSPF is built upon a hierarchy of network components. The highest level of the hierarchy is the Autonomous
System (AS). An autonomous system is defined as a number of networks, all of which share the same routing
and administration characteristics.
An AS can be divided into multiple areas as shown in Figure 17.1 on page 17-2. Each area represents a
collection of contiguous networks and hosts. Areas limit the area to which link-state advertisements are
broadcast, thereby limiting the amount of flooding that occurs within the network. An area is represented in OSPF
by either an IP address or a number.
December 2000
Chapter 17

Configuring OSPF

17 - 1