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regexregex-lookaroundsregex-negation

Select any IP addresses except a group of ones in RegExp

Fairly new to this world (network engineer by carrer).

I need to scrub the configuration files for some routers and need to guarantee that certain servers are configured, but no extra servers are there.

So, let's say I have three servers:

1.1.1.1, 1.1.1.2, 1.1.1.3

and the operator adds a fourth one (2.2.2.2, or any other ip address).

When scrubbing, I need to catch this fourth and signal so it can be marked for removal.

Well, I know how to match any ip address:

(25[0-5]|2[0-4][0-9]|[01]?[0-68-9][0-9]?)\.(25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\.(25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\.(25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)

But how to select any IP address except the ones I need? I tried negative lookahead, but I either did not understand the use of it or used it wrong, because it did nothing to me.

Any hints?

Solution

  • I think this answer will help you solve your problem: Regex not operator You should use as many lookaheads as you have valid IP addresses.