As far as quick and dirty,
grep -Eo '[0-9]+\.[0-9]+\.[0-9]+\.[0-9]+' will work fine.
-06:27:12- Wren:~ :: aldryic % cat iptest
1.2.3.4 no this does not match 3.4.5.6
4.5.6.7 8.9.10.15 ohgoditburns 43.25.11.5
51.13.45.31 and this last one is invalid 301.405.551.987
-06:27:14- Wren:~ :: aldryic % grep -Eo '[0-9]+\.[0-9]+\.[0-9]+\.[0-9]+' iptest
1.2.3.4
3.4.5.6
4.5.6.7
8.9.10.15
43.25.11.5
51.13.45.31
301.405.551.987
Now, the downside is that the simple regex will catch 'invalid' IPs too, like that last one. But unless you're expecting invalid IPs to be in your files that shouldn't be a problem.
EDIT: Instead of
grep [...] filename, you will likely want to do
grep -Eo '[0-9]+\.[0-9]+\.[0-9]+\.[0-9]+' * > report.txt to run the regex through all files in that directory, and dump the results into a .txt file for you.