#!/bin/bash
echo -e '192.168.1.1 foobar\nfoobar 11192.168.1.10000' | \
 grep -E '\b(25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)(\.(25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)){3}\b' # POSIX ERE