Date: Thu, 27 May 1999 14:15:57 -0500 (CDT) From: "Jasper O'Malley" <jooji@webnology.com> To: Dan Langille <junkmale@xtra.co.nz> Cc: freebsd-chat@freebsd.org Subject: Re: Mickey Mouse networking... Message-ID: <Pine.LNX.4.02.9905271359260.30337-100000@mercury.webnology.com> In-Reply-To: <19990527195622.QKUY7623210.mta2-rme@wocker>
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On Fri, 28 May 1999, Dan Langille wrote:
> I understood that ip addresses ending in either 0 or 255 were not to be
> used. They are both used as broadcast addresses. Is that correct?
An IP address with all zeros in the node bits is a network address, and an
IP address with all ones in the node bits is a broadcast address. The
trick is determining what the node bits are, and that's what subnet masks
are for. They're contiguous bitmasks that specify the network bits of a
given IP address.
For instance, 255.255.255.0.0 in binary is
11111111 11111111 00000000 00000000
The ones bits in the mask are network bits, the zeros are node bits. If
I've got the address 10.4.100.255 with a netmask of 255.255.0.0, it looks
like this:
00001010 00000100 01100100 11111111
^---------------^ ^---------------^
network node
The node portion is not all ones or zeros, so it's a valid node address.
Cheers,
Mick
The Reverend Jasper P. O'Malley dotdot:jooji@webnology.com
Systems Administrator ringring:asktheadmiral
Webnology, LLC woowoo:http://www.webnology.com/~jooji
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