Jonathan Angliss schrieb: > Won't match IPv6 addresses, but neither will the original code, and it > matches IP addresses perfectly I believe. My Suggestion for IPv4 is: ^(?!0+\.0+\.0+\.0+$)([01]?\d{1,2}|2[0-2][0-3])\.([01]?\d{1,2}|2[0-4]\d|25[0-5])\.([01]?\d{1,2}|2[0-4]\d|25[0-5])\.([01]?\d{1,2}|2[0-4]\d|25[0-5])$ So 0.0.0.0 (Internet) doesn't match, just as 224.0.0.0/4 (Multicast) and 240.0.0.0/4 (Future Use) as described in RFC3330. (based on the Regex from Mastering Regular Expression, Jeffrey E.F. Friedl) Any further suggestions?