Date: Mon, 16 Aug 1999 23:08:48 -0700 From: Tim Baird <tim@storm.digital-rain.com> To: "David S. Jackson" <dsj@sylvester.dsj.net> Cc: freebsd-questions@freebsd.org Subject: Re: segment, subnet Message-ID: <3.0.2.32.19990816230848.007dbb80@storm.digital-rain.com> In-Reply-To: <19990816205039.E44880@juno.dsj.net>
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At 08:50 PM 16/08/99 -0400, you wrote: >What's the difference between a subnet and a network segment? A subnet is a higher level concept than a segment. A subnet is implemented by partitioning the 32 bit IP address space in such a way as to isolate IP brodcast areas. All hosts with the same net ID (marked by the bit postions in the subnet mask containing a "1") are part of the same subnet - each host must have a unique host ID (marked by the bit positions in the subnet mask containing a "0"). A single host ID is set aside as a broadcast address...usually the host ID that is all '1's. A segment is a lower level concept - down at the physical level. A segment describes a common physical communication channel. With ethernet, a segment is understood as a common collision area...in other words, if a frame from one interface can collide with a frame from another interface, those two interfaces share the same segment. On a vanilla 10Base2 (thin net) setup, the cable is understood as the "segment". With 10BaseT (twisted pair) with a "repeating" hub, each wire attached to the hub combine to form a single segment. On a intelligent/switched hub, you may have the option of isolating ports into separate segments to minimize collisions. Bridges are devices which translate signals from one physical signalling system to another and typically divide the differing physical topologies into segments. You may have multiple segments under one subnet....this is often avoided though You may have multiple subnets on a given segment....this is not typical either. To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-questions" in the body of the message
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