SUMMARY : variable length subnet mask on different interface ...

From: Tim Chan (tim@synoptics.com)
Date: Mon May 24 1993 - 22:39:01 CDT


Hi everyone,

Last week I asked if SunOS support variable subnet mask length on different
interfaces on a single workstation. Thanks to all those who responed, the
answer is NO, if you have the same network address, since SunOS "attaches"
a subnet mask onto the network port of the address, it will work if you
have different network address. That is :

if I have :

interface name IP netmask broadcast
-------------- -------------- ------- ---------
le0 132.143.100.1 0xffffff00 132.143.100.0
le1 132.143.101.17 0xfffffff0 132.143.101.16
le2 132.143.101.33 0xfffffff0 132.143.101.32
le3 132.143.101.49 0xfffffff0 132.143.101.48
bf0 132.143.102.1 0xffffff00 132.143.102.0

it won't work,

but if I have :

interface name IP netmask broadcast
-------------- -------------- ------- ---------
le0 132.143.100.1 0xffffff00 132.143.100.0
le1 132.144.101.17 0xfffffff0 132.144.101.16
le2 132.144.101.33 0xfffffff0 132.144.101.32
le3 132.144.101.49 0xfffffff0 132.144.101.48
bf0 132.143.102.1 0xffffff00 132.143.102.0

it will work, according to rodo@auspex.com.

However, since my only reasons to use variable length subnet mask is to
"collapse" small networks together into a single subnet, (that is
by using 0xfffffff0, I can 14 different subnets of 14 hosts each by
using 132.144.101.xxx), having to obtain or use a new class B address
to make variable length subnet mask works defeats the purpose.

stern@sunne.East.Sun.Com said it only works in 2.1 or later, if at all...

hyder@niwot.scd.ucar.EDU said it is not supported in SunOS thru 4.1.3, and
last time he tried it on Solaris 2.1 still didn't work. And also, said that
almost no host support variable lenght subnet mask, only routes like Cisco
with 9.1 supports it.

        (BTW, this is true, since I've already set up 2 AGS+ with OSPF
        and variable length subnet mask, and it works fine, and that's
        why I inquired about whether the Sun supports it ... Tim)

I guess I am out of luck and have to think again what I should do next.

Thanks to all those who responded :

eckhard@ts.go.dlr.de
rbp@lightnet.com
stern@sunne.East.Sun.COM
rnw@math.Princeton.EDU
paulo@dcc.unicamp.br
miker@il.us.swissbank.com
rodo@auspex.com
ups!upstage!glenn@fourx.Aus.Sun.COM
hyder@niwot.scd.ucar.EDU
vasey@issi.com
lord@andersen.com

Tim Chan
================================ Address ===============================
Tim Chan, Staff Software Engineer, SynOptics Communications Inc.
    (408)-764-1706 fax: (408)-988-8548 4401 Great America Parkway,
email : tim@synoptics.com P.O. Box 58185, Santa Clara, CA 95052-8185



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