Figure 72 A link failure in a statically programmed internetwork can disrupt communications

The effect of this failure is that end systems in networks 10 and 192.168 cannot communicate with each other, even though a valid route exists through Router B! Table 7-2 summarizes the effects of this type of failure on the routing tables.

Table 7-2: Static Routes with a Failed Link

Router

Destination

Next Hop

A

172.16.0.0

B

A

192.168.0.0

C - Unreachable

B

10.0.0.0

A

B

192.168.0.0

C

C

10.0.0.0

A - Unreachable

C

172.16.0.0

B

The lack of any dynamic mechanism prevents Routers A and C from recognizing the link failure. They are not using a routing protocol that would otherwise discover and test the qualities of the links to known destinations. Consequently, they cannot discover the alternative path through Router B. Although this is a valid and usable route, their programming prevents them from discovering it or using it. This situation will remain constant until the network administrator takes corrective action manually.

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