background image
his chapter is the introduction to Open Shortest Path First
(OSPF) areas. It will introduce the term OSPF areas and discuss their role in
OSPF routing. It is very important that you take the time to learn the termi-
nology used in OSPF. Without this knowledge, the remaining sections of the
chapter will be difficult to follow.
Open Shortest Path First
pen Shortest Path First (OSPF) is an open standards routing proto-
col. It is important to recognize that Cisco's implementation of OSPF is a
standards-based version. This means that Cisco based its version of OSPF on
the open standards. While doing so, Cisco also has added features to its ver-
sion of OSPF that may not be found in other implementations of OSPF. This
becomes important when interoperability is needed.
John Moy heads up the working group of OSPF. Two RFCs define
OSPF: Version 1 is defined by RFC 1131, and Version 2 is defined by
RFC 2328. Version 2 is the only version to make it to an operational status.
However, many vendors modify OSPF. OSPF is known as a link-state rout-
ing protocol (link-state routing protocols were discussed in Chapter 2,
"Routing Principles"). The Dijkstra algorithm is used to calculate the short-
est path through the network. Within OSPF, links become synonymous with
OSPF is a robust protocol, and due to the robustness, you must learn
many terms in order to understand the operation of OSPF. The next section
covers the terminology necessary to enable you to understand the many
operations and procedures performed by the OSPF process.
Copyright ©2001 SYBEX , Inc., Alameda, CA