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XGS-4526/4528F/4728F User’s Guide
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CHAPTER 37
OSPF
This chapter describes the OSPF (Open Shortest Path First) routing protocol and
shows you how to configure OSPF.
37.1 OSPF Overview
OSPF (Open Shortest Path First) is a link-state protocol designed to distribute
routing information within an autonomous system (AS). An autonomous system is
a collection of networks using a common routing protocol to exchange routing
information.
OSPF offers some advantages over traditional vector-space routing protocols
(such as RIP). The following table summarizes some of the major differences
between OSPF and RIP.
37.1.1 OSPF Autonomous Systems and Areas
An OSPF autonomous system (AS) can be divided into logical areas. Each area
represents a group of adjacent networks. All areas are connected to a backbone
(also known as area 0). The backbone is the transit area to route packets between
two areas. A stub area, at the edge of an AS is not a transit area since there is
only one connection to the stub area.
Table 113 OSPF vs. RIP
OSPF RIP
Network Size Large Small (with up to 15 routers)
Metrics Bandwidth, hop count, throughput,
round trip time and reliability.
Hop count
Convergence Fast Slow