Routing Table masks

I'm trying to figure out how these routing protocols figure out these masks. The reason being is that I need to advertise BGP routes without using a Null0 static.

So for example. Sometimes if I do a "sh ip route 192.168.100.0" The routing table may show that there it is a 192.168.100.0 /24 with multiple /32 subnets. I assume this is because there are many /32 all over the network and the router is doing some type of summarization

But on other occasions if I have a few interfaces configured with

10.100.10.0 /26 10.100.10.64/26 and 10.100.10.128/26, 10.100.11.0/26 When I do a "sh ip route 10.100.10.0" it will show up as 10.100.10.0 /26 with no other subnets.. Why doesn't it show up as a 10.100.10.0 /23 and list the various subnets?

Please clarify

Thanks in advance

Reply to
ciscortp
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It sounds like it's doing "auto-summary" based on address classes. So

10.100.10.128/26 is a subnet of the Class A address 10.0.0.0/8.
Reply to
Barry Margolin

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