Route Summarization

[mikeg74]

My WAN will be composed of 3 hub sites. Behind each hub site will be multiple branches, so I want to use route summarization to simplify routing tables.

One of my WAN segments (that is, the hub site and the smaller branch offices behind it) will be assigned 172.25.20.0/28 with the subnet mask 255.255.255.240. This breaks that network down into 16 subnets of 14 hosts each.

Since the hub site is a little larger, I want to combine the first two subnets (172.25.20.0 and 172.25.20.16) using the network address 172.25.20.0/27 and a subnet mask of 255.255.255.224.

My question is, is it still possible under this scenario to summarize the entire network using 172.25.20.0/28?

 

[hexn]

172.25.20.0/28 will allow you to use IPs 0-15.

172.25.20.0/27 will allow you to use IPs 0-31.

So the short answer is no.

 

[hexn]

You could do 172.25.20.0/27 to summarize those 2 networks. But you can still break the rest of your IPs up using /28s, such as 172.25.20.32/28 and 172.25.20.48/28 and 172.25.20.64/28 and so on.