Ctrl+H
Find what: ^.+?((?:\d+\.){3}\d+).+$
Replace with: $1
check Wrap around
check Regular expression
DO NOT CHECK . matches newline
Replace all
Explanation:
^ : beginning of line
.+? : 1 or more any character but newline
( : start group 1
(?: : start non capture group
\d+ : 1 or more digit
\. : a dot
){3} : end group, must appear 3 times
\d+ : 1 or more digit
) : end group 1
.+ : 1 or more any character but newline
$ : end of line
Replacement:
$1 : content of group 1 (ie. the IP)