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Date:      Thu, 5 Sep 2002 12:54:10 +0100
From:      Matthew Seaman <m.seaman@infracaninophile.co.uk>
To:        Wayne Pascoe <freebsd@penguinpowered.org.uk>
Cc:        freebsd-questions@FreeBSD.ORG
Subject:   Re: IP Aliases in different subnets
Message-ID:  <20020905115410.GC32849@happy-idiot-talk.infracaninophi>
In-Reply-To: <m2vg5k4pwv.fsf@set.ehsrealtime.com>
References:  <m2vg5k4pwv.fsf@set.ehsrealtime.com>

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On Thu, Sep 05, 2002 at 11:49:36AM +0000, Wayne Pascoe wrote:

> I've got a question about IP aliases in different subnets. Since
> around 4.5-RELEASE, the subnet mask of an IP alias is now supposed to
> be 255.255.255.255. This is fine if all of the aliases are in the same
> subnet as the primary IP address for the adaptor.
> 
> My question is what happens if I have a primary address with a
> different subnet mask to the alias? What should I be using as my
> subnet mask for the alias in /etc/rc.conf
> 
> For example:
> Primary Address - 192.168.1.129  netmask 255.255.255.192
> First Alias     - 192.168.1.193  netmask 255.255.255.224

That's correct.  For each distinct subnet, the first IP address
(whether a primary or alias address) thereon should use the
appropriate netmask for each subnet.  It's the second and subsequent
aliases on a subnet that have to have the 255.255.255.255 netmask.

	Cheers,

	Matthew

-- 
Dr Matthew J Seaman MA, D.Phil.                       26 The Paddocks
                                                      Savill Way
                                                      Marlow
Tel: +44 1628 476614                                  Bucks., SL7 1TH UK

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