OSPF Stub Area - Stubby Area Protocol

The area feature is used in OSPF to divide a large network into small segments. Any changes in one area will not cause any problem in other areas, thus reducing routing table size and processor overhead also.

There are three main types of area:

Stub area
Totally stub area
Not-So-Stubby area (NSSA)

The main purpose of stub area is to block the flooding from AS external advertisements in OSPF and only OSPF injects a default router into a stub area. In this tip we will discuss here only about stub area and the remaining areas will be discussed in the next tips.

Follow the network topology of three different routers in given figure:

There are some common OSPF configuration and Executable commands:

In this example we will not configure router C as stub area because it is backbone router and does not participate in area 1. So we will be concerned here only with router A and router B.

OSPF configuration on Router B as stubby area

In global configuration mode

Router-B(config) # router ospf 1 (Here 1 indicates the process identification number)

Router-B(config-Router) # network 20.0.0.0 0.255.255.255 area 1 (Here 20.0.0.0 indicates the network ID and 0.225.255.255 wildcard mask with area 1)

Router-B(config-Router) # network 30.0.0.0 0.255.255.255 area 0 (Here 30.0.0.0 indicates the network ID and 0.225.255.255 wildcard mask with area 0)

Router-B(config-Router) #area 1 stub (Here 1 indicate the area ID and area 1 is designated as stubby area)

Router-B(config-Router) #exit (exit from ospf 1 on router B)

OSPF configuration on Router A as stubby area

In global configuration mode

Router-A(config) # router ospf 1 (Here 1 indicates the process identification number)

Router-A(config-Router) # network 210.100.10.0 0.0.0.255 area 1 (Here 210.100.10.0 indicates the network ID and 0.0.0.255 wildcard mask with area 1)

Router-A(config-Router) # network 20.0.0.0 0.255.255.255 area 1 (Here 20.0.0.0 indicates the network ID and 0.225.255.255 wildcard mask with area 1)

Router-A(config-Router) #area 1 stub (Here 1 indicate the area ID and area 1 is designated as stubby area)

Router-A(config-Router) #exit (exit from ospf 1 on router A)

Routing Information Protocol (RIP) Configuration

Interior Gateway Routing Protocol (IGRP) Configuration

COMPUTER TIPS