Question

I’m writing a regex for google analytics and I need to block any IP from 156.21.x.x I don’t care about the last 2 octets just the first two. I would like to keep the regex to as few characters as possible as google only allows 255 chars and my regex is already pretty large.

Answer 1

not sure what flavor of regex or what lang your using, but this will work on most regex engines:

156\.21\.\d{1,3}\.\d{1,3}

Of course, this will match invalid ip’s like 156.21.777.888, but if the list your parsing doesnt contain invalid ip addresses, then you should be ok. Or:

156\.21(\.\d{1,3}){2}