Re: Is netmask 255.255.255.254 illigal?

Richard B. Johnson (root@analogic.com)
Sun, 12 Jan 1997 21:03:19 -0500 (EST)


On Sat, 11 Jan 1997, Eugene Kanter wrote:

> Quick one:
>
> kernel 2.0.27
>
> ifconfig eth0 206.42.0.97 netmask 255.255.255.254 broadcast 206.42.0.255
>
> works fine.
>
> kernel 2.1.20
>
> ifconfig eth0 206.42.0.97 netmask 255.255.255.254 broadcast 206.42.0.255
> SIOCSIFNETMASK: Invalid argument
>
> What is wrong?
>
> Did I do something not right or it is kernel bug?
>
>
> Eugene.
>
Depending upon your network (A, B, C, etc.) Your netmask would probably
be 255.255.255.0
255.255.248.0 ... etc. I don't think the last byte would ever be anything
but "0" unless you "own" a very small piece of the address. You want your
address "97" to fit into the mask, i.e., 0 to 97 inverted.

The kernel is now being "pickey" and actually checking these things. Try
255.255.255.0 even though you might not "own" 255 addresses. Just don't
use the ones you don't own.

Cheers,
Dick Johnson
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Richard B. Johnson
Project Engineer
Analogic Corporation
Voice : (508) 977-3000 ext. 3754
Fax : (508) 532-6097
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Email : rjohnson@analogic.com, johnson@analogic.com
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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