Hello Card
BGP Auto-Summary is useful when you have many different subnets that you want to advertise. For example, let’s say you have 250 subnets of the form:
147.52.0.0/24
147.52.1.0/24
147.52.2.0/24
…
and
149.55.26.0/25
149.55.26.129/25
149.55.27.0/25
…
and
152.66.25.30/28
152.66.26.30/28
152.66.27.30/28
These are all discontiguous networks and if you want to advertise them all, you have to explicitly state each one with its subnet mask. That’s 250 network commands. You can use the auto-summary command to simplify configuration and reduce the number of network commands to the classful networks that contain all of the networks you want to advertise.
I hope this has been helpful!
Laz