Re: Why does arp on 2.2.5 return "SIOCSARP: Operation not supported by device"?

Rogier Wolff (R.E.Wolff@BitWizard.nl)
Wed, 14 Apr 1999 10:38:49 +0200 (MEST)


dave@bfnet.com wrote:
> I'm setting up a pair of failover servers on vanilla 2.2.5, and to that end I
> want to use the following script:
>
> --------------------------------------------------------------------------------
> #!/bin/sh
>
> /sbin/ifconfig eth0:1 207.168.228.79 broadcast 207.168.228.127 netmask 255.255.255.192 up
> /sbin/arp -i eth0:1 -s 207.168.228.79 00:10:F3:01:11:24 netmask 255.255.255.192 pub

I'm told that the wonderfully useful netmask-on-published-arp feature
has disappeared.

It seems that one of the Linux developpers (ANK?) said: "I think that
you never need it, so I removed that feature. If you convince me that
you need it, I'll put it back in". (I have this second-hand, so forgive
me if I'm misrepresenting someone ;-)

Ok, So here I go....

At the university we have accumulated about 100 machines in the
group. At first we used bridges to keep out most of the unwanted
traffic, but the broadcasts of the "rest" were using about 10% of our
bandwidth. Bridges let those go through.

So we decided to put in a (linux-)router. Now, ideally, we would
partition the hosts into 4 separate IP ranges, and give each of them
an IP address of the router to use as the default gateway. And we'd
tell the "outside" world of our router. In practise however, we cannot
change the configuration of the 100 machines at the same time, leading
to a long down-time.

Even worse, is the situation on the outside. There are over 2000
computers there, that expect to find our 100 "directly on the
ethernet". There is NO WAY that we can change the configuration on any
of them. There is NO WAY that we can secure a range of IP addreses
outside of the "on the local ethernet" range, so that we could route
through the departemental "default" gateway.

"inside" "outside"
______________
about 100 | |
computers total | linux |
-------------------------| router | about 2000
| | computers +
| | the default
-------------------------| | gateway.
| |----------------
| |
-------------------------| |
| |
| |
-------------------------| |
| |
|______________|

As we ARE trying to move towards the situation where there is simple
routing on the inside, we have published network-arps for the IP
ranges that SHOULD be on one segment. However, the "exceptions to the
rule" were inventoried at the installation time, and new machines are
always assigned a "correct" IP number.

Roger.

-- 
** R.E.Wolff@BitWizard.nl ** http://www.BitWizard.nl/ ** +31-15-2137555 **
*-- BitWizard writes Linux device drivers for any device you may have! --*
------ Microsoft SELLS you Windows, Linux GIVES you the whole house ------

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