Why Do 16-Block IP Blocks Have 13 Usable Addresses?

Stephen Carville stephen at totalflood.com
Wed Dec 15 19:05:22 UTC 2004

On Wed December 15 2004 10:40 am, Will wrote:
> When you are assigned a 16-block (/28) IP address block by an
> ISP, why are only 13 IPs usable?   I was told that the first and
> last addresses in the block are not usable, and the 14th address
> is the gateway.   What are the first and last address used for?

First adddress is the network ID, last address is the broadcast address.

Stephen Carville
Unix and Network Adminstrator
6033 W.Century Blvd.
Los Angeles, CA 90045

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