Path: utzoo!mnetor!uunet!husc6!cmcl2!rutgers!aramis.rutgers.edu!athos.rutgers.edu!hedrick
From: hedrick@athos.rutgers.edu (Charles Hedrick)
Newsgroups: comp.protocols.appletalk
Subject: Re: CAP and Dual interfaced machines.
Message-ID: <495@athos.rutgers.edu>
Date: 23 Dec 87 04:18:04 GMT
References: <488@athos.rutgers.edu> <8712221425.AA13359@columbia.edu> <331@cunixc.columbia.edu>
Organization: Rutgers Univ., New Brunswick, N.J.
Lines: 26

Just for the record, our problem turned out to be that our Sun 4's
don't understand the 4.3-format broadcast address.  We use a subnetted
class B IP address.  The machines for which I have source have all
been modified to understand 128.6.4.255 as a broadcast address.  I
have been unable to get source for the Sun 4, so it still wants to see
128.6.4.0 as the subnetted broadcast address.  The obvious change to
the configuration file causes the gateways to use 128.6.4.0 for the
local broadcast address, and everything works fine.  It turns out that
atis does not support the configuration we would prefer, which
involves using different zones on different interfaces of a
two-interface machine.  Atis is only able to support one zone, and
there can only be one copy of atis on a given machine.  But that's no
big deal for us.

The reason we were able to talk to a Kbox on net 128.6.4 from our
128.6.5 interface but not from our 128.6.4 interface is that 128.6.4
and 128.6.5 are connected by a cisco router.  The cisco router not
only supports directed broadcasts, but it also lets us set a local
broadcast address separately for each interface.  It normalizes all
broadcast addresses that it produces to that address.  We use
255.255.255.255.  So when the broadcast went through the router, the
address got turned into all one's, which the Sun 4 understands.  So we
had the odd situation that local broadcasts didn't work, whereas
broadcasts that went through the router did, because the router was
normalizing the broadcast address to something that all of our
machines understand.