Loopback question

droeun141 · ‎04-29-2010

When would you ever need to use a loopback with anything other than a 32-bit mask?

Federico Coto Fajardo · ‎04-29-2010

Hi,

On a loopback you won't have anything besides the interface itself. So, you can you /32 all times for the single IP.

I've seen loopbacks with other masks i.e. /24 just to keep order (if you don't mind wasting private IPs)

Sometimes when using a policy like a route-map to point to a next-hop instead than to an interface you can have a different mask than /32)

Federico.

Jon Marshall · ‎04-29-2010

droeun141 wrote:

When would you ever need to use a loopback with anything other than a 32-bit mask?

Other than testing when you might want to inject a /24 from a router using a loopback most loopbacks are /32. However if you were using loopbacks to manage devices you may well want to use /32 within each site and then advertise out a /24 to other sites using summarisation.

Jon