blank.gif (43 bytes)

Church Of The
Swimming Elephant

Address Prefix Syntax Connected: An Internet Encyclopedia
Address Prefix Syntax

Up: Connected: An Internet Encyclopedia
Up: Programmed Instruction Course
Up: Subnetting and CIDR
Prev: Binary Hierarchy
Next: A Real Example

Address Prefix Syntax IP address prefixes are patterns which match the first n binary bits of an IP address.

The standard syntax is to write the prefix bits that must match in dotted-quad format, followed by a slash and then the number of bits in the prefix. Any trailing bits, not part of the prefix, are written as zero. If an entire trailing byte is zero, it can be written explicitly, as in, or omitted, as in 128.8/16. Since only the first sixteen bits are significant (in this example), it would be meaningless to specify the remaining sixteen bits, so there's no ambiguity in omitting them.

  • 128.8/16 means to match 10000000 00001000 as the first sixteen bits, and would match,, and, but not
  • 10/10 means to match 00001010 00 as the first ten bits, and would match, and, but not (pay attention to the second number).
  • 208.130.28/24 means to match 11010000 10000010 00011100 as the first twenty four bits, and would match,, and everything in between.

Next: A Real Example

Connected: An Internet Encyclopedia
Address Prefix Syntax


Protect yourself from cyberstalkers, identity thieves, and those who would snoop on you.
Stop spam from invading your inbox without losing the mail you want. We give you more control over your e-mail than any other service.
Block popups, ads, and malicious scripts while you surf the net through our anonymous proxies.
Participate in Usenet, host your web files, easily send anonymous messages, and more, much more.
All private, all encrypted, all secure, all in an easy to use service, and all for only $5.95 a month!

Service Details

Have you gone to church today?
All pages ©1999, 2000, 2001, 2002, 2003 Church of the Swimming Elephant unless otherwise stated
Church of the Swimming Elephant©1999, 2000, 2001, 2002, 2003 is a wholly owned subsidiary of Packetderm, LLC.

Packetderm, LLC
210 Park Ave #308
Worcester, MA 01609