I am using regular expression for checking the subnet masking. I use ajax txtbox with masking value but that is not working, then I switched to a textbox and applying a regular expression for that. unfortunatly that one is also not working.

Can you help me out to give a RE for subnet masking 255.255.255.255

Or any best way to do that?

**Solution**:

I was using masked text box and don't know how to put validation expression.

Finally I found a property of masked text box as validation expression, and there I put the RE and change the property validate to true.

No need to use validator expression explicitly. 

Thanks