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SubjectRe: Is netmask illigal?
On Tue, 14 Jan 1997, Philip Blundell wrote:

> On Sun, 12 Jan 1997, Richard B. Johnson wrote:
> > > ifconfig eth0 netmask broadcast
> > >
> > > works fine.
> > >
> > > kernel 2.1.20
> > >
> > > ifconfig eth0 netmask broadcast
> > > SIOCSIFNETMASK: Invalid argument
> > Depending upon your network (A, B, C, etc.) Your netmask would probably
> > be

> There are quite a lot of cases when you might not want a full class-C
> network. Something like is a perfectly valid subnet mask.
> In this case the last octet is both the `host number' _and_ a couple of
> bits of the subnet mask, so 97 doesn't have to "fit in" to it.
> No. It's BAD BAD BAD<tm> to get your netmask wrong, particularly if you

Now come on! The poor guy had such a bad netmask, probably a typo that had
worked for a long time, but not with the newer kernels, so I tried to help
by telling him a netmask that would at least work. Since ".97" is higher
than 63, lower than 127, he could very well have 1 to 127 or 1 to 254 as
a valid range of addresses. In this case, ".255.0" would be fine at least
until he found more out about his network typogaphy.

If he was able to use anything at all on his local network it was
probably because there was a router on his DEFAULT route that was taking
care of his packets..... Maybe he didn't even have anything on his local
network at all! I could use as my nameserver, have only
the default route to my switch and talk to the world all day. The only
stuff on my local network is WORK, WORK. Maybe I should mask that off.

Dick Johnson
Richard B. Johnson
Project Engineer
Analogic Corporation
Voice : (508) 977-3000 ext. 3754
Fax : (508) 532-6097
Modem : (508) 977-6870
Ftp :
Email :,
Penguin : Linux version 2.1.20 on an i586 machine (66.15 BogoMips).
Warning : It's hard to remain at the trailing edge of technology.

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