126CHAPTER 15: ROUTING CONFIGURATION GUIDE

Configuring OSPF

Among OSPF areas in an AS, one area is different from any other area. Its area ID is

Virtual Link

0 and it is usually called the backbone area. The backbone area is responsible for

 

distributing routing information between none-backbone areas. Therefore, OSPF

 

requires that:

 

 

 

 

All non-backbone areas must maintain connectivity to the backbone area.

 

The backbone area must maintain connectivity within itself.

 

 

In practice, the requirements may not be satisfied due to physical limitations. In

 

this case, configuring OSPF virtual links is a solution.

 

 

A virtual link is established between two ABRs through a non-backbone area and

 

is configured on both ABRs to take effect. The non-backbone area is a transit area.

Network Diagram

Figure 34

Networking diagram for OSPF virtual link

 

 

Switch A

Area 1

 

Switch B

 

 

 

 

 

 

 

 

Vlan-int2

 

 

 

 

 

 

 

 

 

 

 

 

 

Virtual link

 

 

 

 

Vlan-int1

 

Vlan-int1

 

 

 

 

 

 

 

Area 0

 

 

Area 2

 

 

 

 

 

 

 

Device

Interface

 

IP address

Router ID

 

Switch A

Vlan-int1

196.1.1.2/24

1.1.1.1

 

 

 

Vlan-int2

197.1.1.2/24

-

 

Switch B

Vlan-int1

152.1.1.1/24

2.2.2.2

 

 

 

Vlan-int2

197.1.1.1/24

-

Networking and Configure OSPF in the network, which is divided into three areas: the backbone Configuration area and two non-backbone areas (Area 1 and Area 2). Area 2 has no direct Requirements connection to the backbone area; the connection from Area 2 to the backbone

area must go through Area 1. The user hopes to enable Area 2 to communicate with the other two areas.

Based on the user requirements and network environment, configure a virtual link to connect Area 2 to the backbone area.

Applicable Products

Product series

Software version

Hardware version

 

 

 

Switch 5500

Release V03.02.04

All versions

Switch 5500G

Release V03.02.04

All versions

Switch 4500

Release V03.03.00

All versions

 

 

 

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3Com 4210, 5500G, 4200G manual Virtual Link, This case, configuring Ospf virtual links is a solution