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Date: Mon, 8 Apr 2002 12:18:19 -0700 (PDT)
From: John Kozubik <john@kozubik.com>
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To: Jeff Shevlen <jshevlen@passedpawn.com>
Cc: Nick Rogness <nick@rogness.net>, freebsd-questions@FreeBSD.ORG
Subject: Re: IP aliasing
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> > Please note that if the first IP garnered from DHCP is also in the
> > 192.168.0.1/24 subnet, and already has a netmask of 255.255.255.0
> > assigned, the second IP should have a netmask of 255.255.255.255
> >
> 
> 
> Thanks, for the tip.  What is the reason for this?


Any time you have multiple IP addresses in the same subnet configured on a
single machine all subsequent addresses you assign need to have a subnet
mask of 255.255.255.255.  If you give each IP the "real" subnet mask, it
will still function on the network more or less, but you will not be able
to reach that IP from the machine itself.

That is, if you configure 192.168.0.2 / 255.255.255.0 and 192.168.0.3 /
255.255.255.0, you will not (on that machine) be able to ping or ssh to
the second address.

If the alias is in a different subnet, such as 192.168.23.5, and you have
not yet assigned any other IPs in that subnet, you should use the
appropriate subnet mask, such as 255.255.255.192 or whatever.

 -----
John Kozubik - john@kozubik.com - http://www.kozubik.com


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