/etc/networks syntax for subnetted class-C networks

/etc/networks syntax for subnetted class-C networks

Post by Pim Zandberg » Thu, 30 Jul 1998 04:00:00

Our ISP assigned us a full class C network for our internal
networks and a chunk of 8 addresses out of a class C for
our firewalls and routers and stuff.

With netstat -r, the full class-C network shows up by name
on our Linux server, but the second network does not show
up, no matter what I put in /etc/networks.

What's the syntax for /etc/networks if your network is
not standard class A, B or C ?


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1. Class C subnet of Class B network - netmask wrong

I have a hard time believing that this is really a deficiency in Solaris
2.4 (sparc and x86).

There is a 24 bit subnet of a class B network that we want to reach over a
direct ISDN link.  We're using a Pipeline 400 as the router.  It has a
static route set up, which it broadcasts, of (for example),
to this 24 bit subnet of the 16 bit 145.67 class B network.  The rest of
the class B is only accesible over the Internet, which is reachable over a
modem link to the ISP.

Problem is, Solaris seems to only want to give 145.67.89/24 a 16 bit
netmask.  However we try to get the correct mask installed, it always
shows up with a 16 bit netmask, as through the Ascend router.
We've tried using Gated to recieve the broadcast route from the Ascend,
and in.routed, and manually installing the route with "route add net 1".  In every case, netstat -r shows it with a 16
bit netmask.  This is causing quite a headache, since sendmail tries to
reach a host on 145.67.23 (for instance) through the Ascend, when it must
be reached through the modem PPP link over the Internet.  This makes it
open the link for no reason every queue-flush interval, and runs up the
phone bill needlessly, not to mention, failing to deliver the mail.

I've verified that the Ascend has the proper route.  Its own routing
table shows the 145.67.89/24 route to the other end of the ISDN link.
Trying to ping a host on the internet-reachable part of the class B, for
example,, from the Ascend's command line, does not open up the
ISDN link, but instead, gets a ICMP redirect back to itself from the
Solaris x86 host with the modem, which is the right gateway.  But Solaris
thinks it's the wrong route because the netmask if F****D!


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