var reg=/^((1\d\d|2[0-4]\d|25[0-5]|\d{1,2})\.){3}(1\d\d|2[0-4]\d|25[0-5]|\d{1,2})$/

1\d\d 婚配(100-199)
2[0-4]\d 婚配(200-249)
25[0-5] 婚配(250-255)
\d{1,2} 婚配(0-99)
(1\d\d|2[0-4]\d|25[0-5]|\d{1,2}).){3} (0-255.)婚配三次
(1\d\d|2[0-4]\d|25[0-5]|\d{1,2}) (0-255)末端婚配一次