Regular expression:
((2[0-4]/d|25[0-5]|[01]?/d/d?)/.){3}(2[0-4]/d|25[0-5]|[01]?/d/d?)
((2[0-4]/d|25[0-5]|[01]?/d/d?)/.){3}(2[0-4]/d|25[0-5]|[01]?/d/d?)
The red block represents: the first character is 2, the second character is 0 to 4, and the third character is any one-digit number. Indicates 200~249.
Green block represents: the first character is 2, the second character is 5, and the third character is 0 to 5. Indicates 250~255.
The blue block represents: the first character is 0, or 1, or there may be no such character, the second character is any one number, and the third character is any one number, and there may be no such character. Indicates 1~199, there can be leading zeros.
"|" means "or", as long as the meaning of any of the three blocks is satisfied.
The "(" and ")" before and after means this is a set
((2[0-4]/d|25[0-5]|[01]?/d/d?)/.){3}(2[0-4]/d|25[0-5]|[01]?/d/d?)
{3} means repeating three times. For example, "255.255.255."
((2[0-4]/d|25[0-5]|[01]?/d/d?)/.){3}(2[0-4]/d|25[0-5]|[01]?/d/d?)
The last group has the same meaning as above, which is to add the same detection after "."