*BSD News Article 66862


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From: j@uriah.heep.sax.de (J Wunsch)
Newsgroups: comp.unix.bsd.freebsd.misc
Subject: Re: Multiple IP address : what's the limit ?
Date: 25 Apr 1996 20:34:16 GMT
Organization: Private FreeBSD site, Dresden
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References: <317E4080.41C6@marben.be> <4lmub0$f8q@tribune.concentric.net>
Reply-To: joerg_wunsch@uriah.heep.sax.de (Joerg Wunsch)
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Yadra@cris.com (Howard Lamarr) writes:
>I'm currently running 57 aliases on one ethernet card under FreeBSD 2.1R
>with the Apache Web server.  I too, would like to know the upper limit of
>aliases.

There's no true upper limit, they are stored in an (extensible) list.
I've heard a report that someone is running 129 aliases on a single
interface.

>  I would also like to know how to use a different Class C on the
>card from the primary one as we are running out of ips on the first Class
>C.  The ifconfig alias command doesn't appear to work with more than one
>class C.

This is not true.  Actually, the recent abuse of aliasing wasn't
perhaps even anticipated by those who introduced the IP alias code
into BSD, they merely had the idea in mind that somebody could move a
host into a different logical net but still maintain the connectivity
for the old address for some time.

However, you have to configure it once per subnet with the real
netmask, while the aliased addresses need netmask 0xffffffff.  I have
infact already been using aliases to test customer devices (with their
original IP addresses) that have been temporarily linked to our
company's ethernet.  It's really impressing to have this ability. :)

-- 
cheers, J"org

joerg_wunsch@uriah.heep.sax.de -- http://www.sax.de/~joerg/ -- NIC: JW11-RIPE
Never trust an operating system you don't have sources for. ;-)