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Here's the network topology:

enter image description here

Here's the routing table of the R10:

enter image description here

My routing table is right? I just want to make sure I understand the static routing and how it works if one or more nodes fail.

Thanks

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With multiple paths, you need to use metrics (path costs) for the static routes. Otherwise, non-optimal routes may be chosen (e.g. 192.168.6.0/24 via 192.168.6.1) and there may be routing loops (R9 may route back 192.168.6.0/24 via R10).

Metrics for mixed-speed paths can be calculated by selecting a reference speed (e.g. 1 TBit/s) for metric 1 and assign slower links a multiple of that metric/cost (reference speed divided by link speed), e.g.

  1 Tbit/s      1
100 Gbit/s     10
 40 Gbit/s     25
 10 Gbit/s    100
  1 Gbit/s   1000
100 Mbit/s  10000

Subsequent paths are simply added together.

With that and all links 1 Gbit/s, R10 would get

192.168.1.0/24 via 192.168.3.1 metric 2000
192.168.1.0/24 via 192.168.4.1 metric 1000
192.168.1.0/24 via 192.168.5.1 metric 3000

and so on. The router always selects the path with the lowest metric.

Of course, this very quickly becomes very cumbersome which is a good reason to run a routing protocol like OSPF that'd take care of all that. Note that you've only added the link segments to your diagram - end-node segments may be missing, most obviousy behind R11 and R12.

Also, static routes like that don't handle some failures very well (if R11 is down, traffic for 192.168.6.0/24 is still routed up to R8). Some failures could also cause a routing loop (R8 fails and R7-R10 may start looping).

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  • Thank you very much. Yes I plan to use OSPF but I wanted to know in the case of static route.
    – qyqur
    May 30 at 14:51

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