[384] in linux-net channel archive
Re: Feature/hack for multi-homed hosts (esp. ifconfig alias)
daemon@ATHENA.MIT.EDU (Mister Linux)
Sat May 27 20:12:49 1995
To: linux-net@vger.rutgers.edu
In-reply-to: Your message of "27 May 1995 19:52:00 GMT."
<hpa.2fc78243.Allah.u.Abha@asgard.yggdrasil.com>
Date: Sun, 28 May 1995 01:34:29 +0200
From: Mister Linux <linux@goofy.zdv.uni-mainz.de>
H. Peter Anvin wrote on linux-net:
>
>This isn't a problem, at least not IMHO. In fact, this is *exactly*
>what the program wants - bind to all existing IP local addresses.
>
So? I don't think so. Just to illustrate the problem:
Our public server (a 4-CPU DEC Sable running OSF/1) has two interfaces,
Ethernet and FDDI, with 3 addresses bound to them.
Ethernet <-> kralle.zdv.Uni-Mainz.DE
FDDI <-> kralle.zdv.Uni-Mainz.DE
and infosys.zdv.Uni-Mainz.DE (= FTP/WWW/Gopher/WAIS-Server)
The idea behind this arragement is that in case of a breakdown, just plug
the (external) disks to the backup machine and tell its FDDI interface
to handle all requests for infosys as well...
Now where is the problem? Any NFS mount by a Linux- or NetBSD-host of one
of infosys' filesystems gets a time-out. Just those two OS ...
So we traced with a Sniffer and what happens is: The NFS server processes
on the Sable do not remember by which IP-Address they were contacted and
then answer over their default interface, the Ethernet!
Both Linux and NetBSD apparently assume that they are being spoofed and
discard the packages silently ... timeout. All other OS in our zoo (HP/UX,
OSF/1, Irix, SPP-UX, Solaris, SunOS, AIX , Ultrix, SINIX and SCO) can work
with this setup without any apparent problems.
Only work-around is to forget the fail-safe scheme and use the IP-Address of
the Ethernet. (BTW the same happens with our AIX-based AFS-Server, he has two
IP addresses for his two interfaces - again one Ethernet and one FDDI)
We were thinking of starting more NFSD's on the Sable and then use adb to
patch the socket structures with the distinct addresses, but so far lack of
time has prevented that lunatic plan. But who knows if we ever get desperate
enough, we might try it ...
Dominik
