Friday, November 8, 2013

remember routes have masks

in a couple of previous posts (bgp and old loopbacks never die), I hinted that routers allow routes with overlapping masks and will display longer mask routes by default. For example **sho ip route 10.40.0.97 Routing entry for 10.32.0.0/11 Known via "bgp 65013", distance 20, metric 0 you see the /11 summary however you can add the subnet mask sho ip route 10.40.0.97 255.255.255.255 % Subnet not in table to get a more accurate view. It is important to closely examine the results of a display to see what route is REALLY there, as was described in the loopback post routers will have a /30 and a /32 that overlap. So use the subnet mask in the route display if it is important.

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