Avaya P3343T-ML manual OSPF Open Shortest Path First Configuration, OSPF Overview

Chapter 12 Avaya P330 Layer 3 Features

OSPF (Open Shortest Path First) Configuration

OSPF Overview

OSPF is a routing protocol developed for IP networks based on the shortest path first or link-state algorithm. It was introduced to overcome the limitations of RIP in increasingly complex network designs.

OSPF is based on the cost of a particular path. In contrast, RIP uses hops as a path criterion. Also, updates are sent on a “need to know” basis rather than every 30 seconds as with RIP.

The advantage of shortest path first algorithms is that they result in smaller more frequent updates everywhere. They converge quickly, thus preventing such problems as routing loops and Count-to-Infinity (when routers continuously increment the hop count to a particular network). This stabilizes the network.

The disadvantage of shortest path first algorithms is that they require a lot of CPU power and memory.

Routers use link-state algorithms to send routing information to all nodes in an internetwork by calculating the shortest path to each node. This calculation is based on a topography of the Internet constructed by each node. Each router sends that portion of the routing table (keeps track of routes to particular network destinations) that describes the state of its own links, and it also sends the complete routing structure (topography).

The P330 supports the OSPF routing protocol. The P330 can serve as an OSPF Autonomous System Boundary Router (ASBR) by configuration of route redistribution. The P330 can be installed in the OSPF backbone area (area 0.0.0.0) or in any OSPF area that is part of a multiple areas network. However, the P330 cannot be configured to be an OSPF area border router itself.

The P330 supports the equal-cost multipath (ECMP) feature which allows load balancing by splitting traffic between several equivalent paths.

While OSPF can be activated with default values for each interface using a single command, many of the OSPF parameters are configurable.

For a detailed description of OSPF, refer to the OSPF standards and published literature.

134 Avaya P334T-ML User’s Guide