Is specifying meaningless bits valid syntax in CIDR notation? For instance, the netmask of is In this case, the last two octets (00001101 00000000) are meaningless because any value between and (inclusive) is in range. I'm curious what's considered valid in CIDR notation.

  • 1
    Hello and welcome. They're not "meaningless bits", they're "host bits" !
    – jonathanjo
    Jul 16 '19 at 16:31

Yes it's a valid syntax. Every host on a network has an IP address, and it's also important to know what subnet it's a part of. You need that information to configure the host. So tells you what the host IP is and also what the subnet is.

If we follow your idea to the logical extreme, everything is in the range of, so we don't need to specify IP addressing at all.


When you specify an address longer than the bits in the mask, you are generally referring to a host address. In your example, would be a host on the network. That gives you the host address and mask (similar to, except in shortened form), from which you can derive all type of network information. See this two-part answer for the details.

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