26. Irregular area virtual link of OSPF configuration experiment 09/22 Update SLTechnology News&Howtos

26. Irregular area virtual link of OSPF configuration experiment

2025-09-22 Update From: SLTechnology News&Howtos shulou NAV: SLTechnology News&Howtos > Network Security >

Shulou(Shulou.com)06/01 Report--

1. Experimental Topology

After OSPF is configured as shown in the topology, R5 in area2 does not have routes to area3, area0, and area1 because there is an area1 between area2 and area0. For this reason, we can establish a virtual link on R3 and R4.

2. Experimental configuration

R1 configuration

Interface Loopback0

Ip address 1.1.1.1 255.255.255.0

Interface Serial0/0

Ip address 12.1.1.1 255.255.255.0

Router ospf 110

Router-id 1.1.1.1

Network 1.1.1.0 0.0.0.255 area 3

Network 12.1.1.0 0.0.0.255 area 3

R2 configuration

Interface Loopback0

Ip address 2.2.2.2 255.255.255.0

Interface Serial0/0

Ip address 12.1.1.2 255.255.255.0

Interface Serial0/1

Ip address 23.1.1.2 255.255.255.0

Router ospf 110

Router-id 2.2.2.2

Network 2.2.2.0 0.0.0.255 area 0

Network 12.1.1.0 0.0.0.255 area 3

Network 23.1.1.0 0.0.0.255 area 0

R3 configuration

Interface Loopback0

Ip address 3.3.3.3 255.255.255.0

Interface Serial0/0

Ip address 34.1.1.3 255.255.255.0

Interface Serial0/1

Ip address 23.1.1.3 255.255.255.0

Router ospf 110

Router-id 3.3.3.3

Network 3.3.3.0 0.0.0.255 area 0

Network 23.1.1.0 0.0.0.255 area 0

Network 34.1.1.0 0.0.0.255 area 1

R4 configuration

Interface Loopback0

Ip address 4.4.4.4 255.255.255.0

Interface Serial0/0

Ip address 34.1.1.4 255.255.255.0

Interface Serial0/1

Ip address 45.1.1.4 255.255.255.0

Router ospf 110

Router-id 4.4.4.4

Log-adjacency-changes

Network 4.4.4.0 0.0.0.255 area 1

Network 34.1.1.0 0.0.0.255 area 1

Network 45.1.1.0 0.0.0.255 area 2

R5 configuration

Interface Loopback0

Ip address 5.5.5.5 255.255.255.0

Interface Serial0/1

Ip address 45.1.1.5 255.255.255.0

Router ospf 110

Router-id 5.5.5.5

Log-adjacency-changes

Network 5.5.5.0 0.0.0.255 area 2

Network 45.1.1.0 0.0.0.255 area 2

3. Configure OSPF virtual links

At this point, neither R1 nor R5 has routes to each other. We will make the following changes on R3 and R4

R3 configuration

Router ospf 110

Area 1 virtual-link 4.4.4.4

R4 configuration

Router ospf 110

Area 1 virtual-link 3.3.3.3

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