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Path: euryale.cc.adfa.oz.au!newshost.anu.edu.au!harbinger.cc.monash.edu.au!nntp.coast.net!news.kei.com!newsfeed.internetmci.com!news.ac.net!news.serv.net!not-for-mail From: zeno@serv.net (Sean T. Lamont) Newsgroups: comp.unix.bsd.freebsd.misc Subject: Re: Can't traceroute to virtual hosts Date: 19 May 1996 00:56:23 -0700 Organization: ServNet Internet Services, Seattle, WA Lines: 62 Message-ID: <4nmk77$17o@itchy.serv.net> References: <4mhaeg$f8@venus.os.com> <4nd1nv$1cn@anorak.coverform.lan> <4nhq8j$f5p@itchy.serv.net> <4nljp0$1l5@uriah.heep.sax.de> NNTP-Posting-Host: itchy.serv.net In article <4nljp0$1l5@uriah.heep.sax.de>, J Wunsch <joerg_wunsch@uriah.heep.sax.de> wrote: >zeno@serv.net (Sean T. Lamont) wrote: > >> >The mask should be 0xffffffff - meaning that anything on this network can >> >be reached down this interface.... ie. only that machine. >> >> From a TCP/IP standpoint, this makes little sense. All bits are significant >> for the network, none for the host? What about IP broadcast for that >> subnetwork? > >It is already caught by the `primary' address of this interface. Only >the `secondary' address(es) should get 0xffffffff. (I.e., unlike >filename hard links, the different aliases are not uniform each >other.) ah, but since you're specifying 0xffffffff, the primary address isn't on the same net as the 'aliased' address. Any subnetwork should have one broadcast per net, which since you're specifying a 32-bit subnet mask, indicates that there should be one broadcast address per IP#. As a matter of fact, there shouldn't even be a way to route packets between that net and the other nets on your class C, but by some amount of alchemy, it works. > >From a TCP/IP standpoint, alias addresses are a DON'T DO anyway. :) > >-- I'm not sure I agree. If you think about a machine with multiple physical ethernet interfaces on the same box, each having a separate interface (ed0,ed1, etc.), it's pretty straightforward. The only major leap of faith is to say "ok, ed0.0 and ed0.1 are really on the same ethernet interface. As a matter of fact, this might be more straightforward way to do IP aliasing under FreeBSD, the ability to create (to borrow the term from cisco) a "subinterface" ed0.0, ed0.1,ed0.2, which are separate from ed0 and behaves like a real interface in every respect. As a further objection, I would maintain that EVERY tcp/ip connection on a unix box has IP "aliases". Usually one for the ethernet, lo0 for your loopback, and any slip interfaces you're using. Try configuring apache for a VirtualHost on 127.0.0.1 ; it works on every unix box I've worked on, regardless of whether they support ip aliasing or not! for whatever reason, using 0xffffff00 and routing that IP# to 127.0.0.1 works just fine for me , and I will continue to use it. -- Sean T. Lamont, President / CEO, Abstract Software (ServNet) - Internet access * WWW hosting * TCP/IP * UNIX * NEXTSTEP * WWW Development - email: lamont@abstractsoft.com WWW: http://www.serv.net "...There's no moral, it's just a lot of stuff that happens". - H. Simpson