What's 10.0.40.1/22 netmask? How is this number (the 22) calculated? Can you use this style to indicate subnet mask 255.255.0.0, for example?

22 means 22 bits. Each of the 4 parts of the dotted quad number is a byte, 8 bits, and /22 means 22 1's and the rest zeros i.e. 22 1's = 8+8+6 1's = 11111111.11111111.11111100.00000000 which is 255.255.252.0 if you do your binary conversions. So 255.255.0.0 would be /16 and 255.255.255.0 would be /24 by the same notation. And this notation's a lot less brainfag. -- ******************************************************************************** All mail sent and received may be examined to prevent transmission of unacceptable material. Wellington College does not accept responsibility for email contents. Problems to postmaster@wellington-college.berks.sch.uk. Website: http://www.wellington-college.berks.sch.uk ********************************************************************************