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Given the following diagram, I've modified the static routing tables with an entry for each router of the other two, through the serial interface, and everything works fine.

What should I change so that if 192.168.23.4 /30 would stop working, I could still reach 192.168.22.1 from 192.168.21.1 through 192.168.20.1?

Thanks in advance! network diag

2
  • If you have it in Packet Tracer, then try it. Just shut down the link.
    – Ron Maupin
    Mar 29 '17 at 21:12
  • Did any answer help you? If so, you should accept the answer so that the question doesn't keep popping up forever, looking for an answer. Alternatively, you could provide and accept your own answer.
    – Ron Maupin
    Aug 27 '17 at 17:31
3

The simplest solution would be to add a dynamic routing protocol such as RIP, EIGRP or OSPF. Then raise the Administrative Distance of the static routes so the dynamically learned routes are preferred. These static routes with the higher administrative distance become floating static routes.

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With static routing you would need to manually enter backup routes into each device with a higher administrative distance. This will prevent the backup route from being loaded into the routing table unless the primary route were to fail.

This is obviously a big hassle, and becomes a bigger one when you add even more networks to the mix which is why dynamic routing protocols are so useful.

0

A default route can be configured on the router, if no route matches, the default route will be used. This would be a simple way to re route a packet when a link goes down. A static route of 0.0.0.0 0.0.0.0 s0/0/1 can be configured. If the incoming packet does not match a route in table the default route is used. If s0/0/0 goes down then s0/0/1 becomes the outing interface (in the example used). The default route matches all packets without a route in the table. May not be best solution but would work I think =)

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