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.



With multiple paths, you need to use metrics (path costs) for the static routes. Otherwise, non-optimal routes may be chosen (e.g. via and there may be routing loops (R9 may route back 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 via metric 2000 via metric 1000 via 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 is still routed up to R8). Some failures could also cause a routing loop (R8 fails and R7-R10 may start looping).

  • 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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