Date: Wed, 28 Feb 2001 01:44:14 -0500 From: "Matthew Emmerton" <matt@gsicomp.on.ca> To: "Wes Peters" <wes@softweyr.com>, "Josef Karthauser" <joe@tao.org.uk> Cc: "Rogier R. Mulhuijzen" <drwilco@drwilco.nl>, "Jonathan Graehl" <jonathan@graehl.org>, <freebsd-net@FreeBSD.ORG> Subject: Re: Quick question about IP aliasing Message-ID: <010d01c0a151$ddfca980$1200a8c0@gsicomp.on.ca> References: <NCBBLOALCKKINBNNEDDLAEJIDLAA.jonathan@graehl.org> <001501c0a070$3a14d900$1200a8c0@gsicomp.on.ca> <4.3.2.7.0.20010227070424.00d25c10@mail.bsdchicks.com> <20010227194556.C737@tao.org.uk> <3A9C997F.51F81F8D@softweyr.com>
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> Josef Karthauser wrote: > > > > On Tue, Feb 27, 2001 at 07:16:14AM +0100, Rogier R. Mulhuijzen wrote: > > > > > > >The point is that you need to use a netmask of 255.255.255.255 for aliased > > > >IPs on FreeBSD, regardless of the alias of the primary (non-alias) IP. > > > > > > Everybody is saying use 255.255.255.255 for an alias. Noone is giving > > > reasons why. > > > > I don't understand this either. To my mind it's a bug if it doesn't > > work with the full netmask for an IP alias address. > > Because if you don't, it won't work. ifconfig(8) may not be telling the > entire truth here: > > alias Establish an additional network address for this interface. This > is sometimes useful when changing network numbers, and one wishes > to accept packets addressed to the old interface. If the address > is on the same subnet as the first network address for this in- > terface, a netmask of 0xffffffff has to be specified. > > Somebody should look to see if the man page is true, or if you have to use > a netmask of 0xffffffff for all aliases. I just had a short off-line conversation with Luigi Rizzo about this, and the manpage is true. (You must use a netmask of 0xffffffff for aliases on the same subnet as the primary IP, otherwise you use the appropriate netmask for the alias IP.) Since the more intuitive method is to use the 'appropriate' netmask all the time (and is what AIX and SCO do), I'm looking into seeing what it would take to add this functionality to FreeBSD. -- Matt Emmerton To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-net" in the body of the message
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