use regular expressions to find IP addresses

Good site for building regular expressions
https://regexr.com/

How to find IP the quick way and the exact way
https://www.regular-expressions.info/ip.html

Find IP (this will find 999.999.999.999 but you might not care
\b\d{1,3}\.\d{1,3}\.\d{1,3}\.\d{1,3}\b

Below I was looking for 192.168.x.x
(192.168.)\d{1,3}\.\d{1,3}

Notes:
\b allows you to perform a "whole words only" search using a regular expression in the form of \bword\b. A "word character" is a character that can be used to form words. All characters that are not "word characters" are "non-word characters".

\d look for a digit

\d{1,3} look for between 1 to 3 digits

(192.168.) look for a group "192.168."

Example 1

Look for some thing with any character "." 

that is 1 or more long "{1,}"

followed by a new line (\n)

followed by any number of white space "(\s+)"

followed by IP address (simple) "(\d{1,3}\.\d{1,3}\.\d{1,3}\.\d{1,3})"

(.{1,})(\n)(\s+)(\d{1,3}\.\d{1,3}\.\d{1,3}\.\d{1,3})

White space characters

\t (tab)

\n (newline)

\s (any white space)

\s+ (any number of white space) 

Example 2

Looks for something(word) with any character 1 or more

any white space

IP address 

(.{1,})(\s)(\d{1,3}\.\d{1,3}\.\d{1,3}\.\d{1,3})

Capture groups

(\n)(\t)

$1 = newline

$2 = tab