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Case study of OSPF Network Fault treatment

The network topology is shown in figure 11.1. The network plan is as follows:

The interconnection address of R1 and R2 is: 10.0.0.0, the interconnection address of R2 and R3 is: 20.0.0.0, the interconnection address of R3 and R4 is: 30.0.0.0, the interconnection address of R4 and R1 is: 40.0.0.0.

N use the Loopback0 interface address of the router as the Loopback0:1.1.1.1/32,R2 of Route-id,R1, the Loopback0:4.4.4.4/32 of Loopback0:2.2.2.2/32,R3 of Loopback0:3.3.3.3/32,R4

N uses the Loopback interface of the router to simulate the client host address. The hosts on the R3 router with four network segments are: 192.168.0.0, 192.168.1.0, 192.168.2.0, and 192.168.3.0, respectively.

Figure 11.1 Network Topology Diagram of BENET Company

After configuring route summarization on ABR, it is found that the R1 router can still learn detail routing, which makes it impossible for packets to form load balancing only through detail routing. Please check the configuration to resolve the problem.

R1 configuration

Router ospf 1

Router-id 1.1.1.1

Network 1.1.1.1 0.0.0.0 area 0

Network 10.0.0.0 0.0.0.3 area 0

Network 40.0.0.0 0.0.0.3 area 0

R2 configuration

Router ospf 1

Router-id 2.2.2.2

Area 1 range 192.168.0.0 255.255.252.0

Network 2.2.2.2 0.0.0.0 area 0

Network 10.0.0.0 0.0.0.3 area 0

Network 20.0.0.0 0.0.0.3 area 1

R3 configuration

Router ospf 1

Router-id 3.3.3.3

Network 3.3.3.3 0.0.0.0 area 1

Network 20.0.0.0 0.0.0.3 area 1

Network 30.0.0.0 0.0.0.3 area 1

Network 192.168.0.0 0.0.0.255 area 1

Network 192.168.1.0 0.0.0.255 area 1

Network 192.168.2.0 0.0.0.255 area 1

Network 192.168.3.0 0.0.0.255 area 1

R4 configuration

Router ospf 1

Router-id 4.4.4.4

Network 4.4.4.4 0.0.0.0 area 0

Network 30.0.0.0 0.0.0.3 area 1

Network 40.0.0.0 0.0.0.3 area 0

First, view the routing table of R1 as follows:

192.168.0.0/32 is subnetted, 1 subnets

O IA 192.168.0.1 [110/3] via 40.0.0.1, 00:25:05, FastEthernet1/0

192.168.1.0/32 is subnetted, 1 subnets

O IA 192.168.1.1 [110/3] via 40.0.0.1, 00:25:05, FastEthernet1/0

192.168.2.0/32 is subnetted, 1 subnets

O IA 192.168.2.1 [110/3] via 40.0.0.1, 00:25:05, FastEthernet1/0

192.168.3.0/32 is subnetted, 1 subnets

O IA 192.168.3.1 [110/3] via 40.0.0.1, 00:25:05, FastEthernet1/0

O IA 192.168.0.0/22 [110/3] via 10.0.0.2, 00:25:05, FastEthernet0/0

By looking at the routing table, it is found that the R1 router learns both the detailed routing and the detailed routing, and then looks closely at the next hop of the routing table and finds that R2 publishes the summarized route, while the detailed route is published by R4. This shows that the failure is caused by the summary configuration of the R4 router.

Check the configuration of the R4 router and find that route summarization is not configured. As a result, detailed routes before summarization can be learned in the routing table, resulting in packets being forwarded only from detail routes.

Configure the area 1 range 192.168.0.0 255.255.252.0 command on R4 to achieve route summarization, and look at the routing table of the R1 router again. R1 has learned route summarization and achieved load sharing, as follows:

O IA 192.168.0.0/22 [110/3] via 40.0.0.1, 00:00:10, FastEthernet1/0

[110/3] via 10.0.0.2, 00:00:10, FastEthernet0/0

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