CIDR Quick Question

[jimslim]

I'm trying to create a few rules around some IP's I want to filter and redirect away from my VPN on my ASUS router.

The problem is I don't know all the exact IP's but do know the general format and would be fine with a few false positives from using a more general rule.

They are all in the: 52.xxx.xxx.xxx and 54.xxx.xxx.xxx.xxx range. Is there a way to include all those via a CIDR line?

From my research I was thinking 52.0.0.0/8 & 54.0.0.0/8 but it doesn't seem to be doing what I would expect?

 

[jimslim]

Actually I think what I used is right after playing with a few things.

 

[slidermike]

Yup, if you want to block all those IPs (52.x.x.x & 54.x.x.x) then you have it correct.
The /8 means respect the first octet and dont worry about the last 3 octets.