Date: Tue, 27 Feb 2001 22:58:15 -0500 From: "Matthew Emmerton" <matt@gsicomp.on.ca> To: "Luigi Rizzo" <luigi@info.iet.unipi.it>, "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: <007901c0a13a$b4480dd0$1200a8c0@gsicomp.on.ca> References: <200102280156.CAA29214@info.iet.unipi.it>
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> > On Tue, Feb 27, 2001 at 07:16:14AM +0100, Rogier R. Mulhuijzen wrote: > > > > > > > [ Matt Emmerton 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. > > no this is incorrect. you just have to make sure that the aliased > IP&mask do not generate info which is already in the routing table. > E.g. if your primary addr is 1.2.3.4/24 , an alias of 1.2.3.5/24 will > give a warning, but an alias of 1.2.4.4/24 will not, and most likely even > 1.2.3.5/25 will not. I'm just reiterating what I was told 1.5 years ago when I complained that the following setup wouldn't work: Primary IP: 192.168.0.1/255.255.255.0 Aliased IP: 192.168.0.10/255.255.255.0 With this setup, I could not ping, traceroute or connect to the aliased IP. In order to make the aliased IP functional, I had to use a netmask of 255.255.255.255 -- a fact which I find totally confusing and counter-intuitive, but one that seems to work. > > > Everybody is saying use 255.255.255.255 for an alias. Noone is giving > > > reasons why. Exactly. I never got a good answer to this when I first stumbled upon it, and I still haven't. All I know is that this is the way it needs to be done in order for things to work properly. -- Matt Emmerton To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-net" in the body of the message
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