G'day ilcylic,

While it may be possible to use 'grep -P ...', I suspect using 'perl ...' (on the command line) would be a lot simpler.

Regexp::Common provides often-used regexes; Regexp::Common::net has regexes for IP addresses.

Using this module, I'd eliminate lines matching /^$RE{net}{IPv4}/ first; then attempt to match /^\S+\s+.*?$RE{net}{IPv4}/.

For use on the command line: 

$ perl -MRegexp::Common=net -wnE '/^$RE{net}{IPv4}/ and next; /^\S+\s+
+.*?$RE{net}{IPv4}/ and say'
127.0.0.1aaa 127.0.0.1
256.0.0.1aaa 127.0.0.1
256.0.0.1aaa 127.0.0.1

aaa 127.0.0.1
aaa 127.0.0.1

[download]

Having tested that solution, I noticed your update with examples. For IPv4, all of the octets should be in the range 0-255. I suspect you generated quick-and-dirty examples (by running along the number keys) which has produced invalid IP addresses. Changing 456 to 156 and 654 to 154, the same one-liner matches the way you want: 

$ perl -MRegexp::Common=net -wnE '/^$RE{net}{IPv4}/ and next; /^\S+\s+
+.*?$RE{net}{IPv4}/ and say'
ADMIN__SANDRO_DESK="123.156.78.90"   #  ilcylic Desktop
# ADMIN__SANDRO_DESK="123.156.78.90"   #  ilcylic Desktop
# ADMIN__SANDRO_DESK="123.156.78.90"   #  ilcylic Desktop

# 06/06/15    SR    Chgd SANDRO 121.123.154.99
# 06/06/15    SR    Chgd SANDRO 121.123.154.99

[download]

— Ken

In reply to Re: Seeker of Regex Wisdom (strings which don't form specific patterns) by kcott
in thread Seeker of Regex Wisdom (strings which don't form specific patterns) by ilcylic

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