SUMMARY: A BETTER SUMMARY: different netmasks w/ two interfaces

From: Mark Natoli (mnatoli@npac.syr.edu)
Date: Fri Oct 01 1999 - 13:26:49 CDT


NOTE:
This is a second summary to this problem.

ORIGINAL PROBLEM:
  I have an Ultra-2 with a FDDI interface and Fast Ethernet interface.
This machine is attached to two separate networks but no routing is done.
All is fine when both cards exist using the same netmask. But when I want
to change the hme0 netmask from 255.255.255.0 to 255.255.255.224 without
changing the mask of the nf0 interface I find this impossible using only
the /etc/inet/netmasks.

/etc/inet/netmasks
  131.230.19.0 255.255.255.224
  131.230.0.0 255.255.255.0

where the hme0 is 131.230.19.2
and the nf0 is 131.230.8.2

  I have also tried including 131.230.8.0 255.255.255.0 in the netmasks
file as well as most logical combinations/orders that I could think.

ADVICE I RECEIVED:
Many thanks to Martin Oksnevad and Eric at Sun.
With out Martin's insistence that it was possible I would have given up.

>From a document sent Eric at Sun:
"The 2.6 kernel has changed to support VLSM. It is now possible to combine
the RFC-950 and RFC-1519 form of subnet masks in the netmasks file.
The network address should be the "SUBNETTED" address NOT the standard
network number based on the hosts ip address. (see man page for netmasks)"

SOLUTION
  I see what my problem is, in my original question I did not include the
correct details because the two masks in this scpecfic case are really
255.255.255.192 and 255.255.255.224. The second one is not 255.255.255.0

  So this works easily
131.230.0.0 255.255.255.224
131.230.19.0 255.255.255.0

  But this doesn't (which is what I want)
131.230.0.0 255.255.255.224
131.230.19.0 255.255.255.192

  In order to fix this you need to do this:

i.e.
ip's
131.230.19.135
131.230.8.175

netmasks
131.230.19.128 255.255.255.192
131.230.8.160 255.255.255.224

-Mark

Mark Natoli
Systems and Network Administrator
Northeast Parallel Architectures Center, Syracuse University
mnatoli@npac.syr.edu



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