Only extract valid IPv4 addresses.

echo '01-01-1970 - Some text about yo mama 255.168.001.255 - fo realz' | grep -P "(?:\b(?:\.)?[2][0-5][0-5](?:\.)?\b|\b(?:\.)?[0-1]\d\d(?:\.)?\b|\b(?:\.)?\b\d\d\b(?:\.)?\b|\b(?:\.)?\b\d\b(?:\.)?\b){4}"