Broadcasting woes on Vax 4.2 Unix

[romig at osu-eddie.UUCP]

From: romig (Steve Romig)

Here's the situation:  we have 3 Suns and a Vax 780 on an Ethernet.  All
four are running variations of 4.2 BSD Unix.  For the most part, everything
works just great.  We can telnet about, rlogin, etc.  A while ago, someone
here started messing about with broadcast datagrams on the net.  They found
that they could get it all to work on the Suns, but not on the Vax.  The
receiving program does not receive broadcast packets sent from the Suns.  No
one can receive the broadcast packets sent from the Vax.  

So he started looking at the sources for other odds and ends, trying to
figure out how broadcast stuff was supposed to work.  In particular, he
looked at "rwhod" to see what it did.  As a part of this, we decided to go
ahead and install rwhod on the system for grins (we hadn't bothered with
it when we first put everything on the net).  Lo and behold, rwho and co.
don't work either.  

Other strange anamolies:  on the Suns, typing "/etc/ifconfig ec0" gives
me "flags=63<UP,BROADCAST,NOTRAILERS,RUNNING>".  On the Vax, I see
"flags=21<UP,NOTRAILERS>".  On both the Suns and the Vax we configure
the interface with the line "/etc/ifconfig ec0 `hostname` -trailers up".

Other info: we are using a 3com ethernet board in the Vax.

Questions:

1. why doesn't rwho and co. work, and more generally, why can't we get
   broadcast datagrams to work?

2. why doesn't ifconfig on the Vax tell us that the interface is RUNNING
   and BROADCAST?  How can we convince it to be RUNNING and BROADCAST?
   What does it mean when it claims RUNNING, anyway?

Answers or hints would be greatly appreciated.  I'll summarize to
the net if I hear anything useful.

--- Steve 

romig at ohio-state on CSNet
cbosgd!osu-eddie!romig on UUCP