KVC@ENGVAX.SCG.HAC.COM (Kevin Carosso) (07/17/87)
If anyone's still interested, here's the outcome of the problem I reported
to the list a while ago with receiving ethernet broadcasts on
a VAXstation-2000.
It turns out that DEC filters out broadcasts on "newer ethernet interfaces".
I assume this is a change to the device driver somewhere. If you want to
receive broadcasts and multicasts, you must enable them for your protocol
type. You can use the NMA$C_PCLI_MCA or NMA$C_PCLI_MLT to do so. The former
is what DEC recommends. It works fine for multicast addresses. I gave
it a try for the ethernet broadcast address (FF-FF-FF-FF-FF-FF) but it was
unhappy. So, for broadcasts you have to use MLT. It means putting something
like:
.word NMA$C_PCLI_MLT
.long NMA$C_STATE_ON
in the nasty structure you send to the ethernet device when you start up
your protocol. Both are documented in the "I/O User's Guide", so look it
up if you need it. (though I never found documention indicating that
the driver REQUIRED you to do so on the -2000)
In my case (fixing CMU/Tek TCP/IP for the VS-2000) I enabled MLT for the
ARP protocol, but disabled it on IP. If there's a need to accept ethernet
broadcasts on IP, could someone let me know? It works just fine on the
VS-2000 now.
Do the BI ethernet controllers (DEBNT clunker and DEBNA (?) new widget)
do the same thing as the DESVA on the VS-2000? If so, you'll need my fixes.
To the people who commented that the CMU stuff worked on their VS-2000,
maybe CMU had the fix in a later release? Alternately, if you were always
going from the VMS VS-2000 *to* a UNIX 4.2 or 4.3 machine, that will work
anyway because UNIX doesn't need to ARP since it saves the ARP address when
it gets the ARP from the VS-2000 who started the connection. The CMU stuff
should probably do that too, it saves on the number of broadcasts on the
net. I will see about adding that when I have some time.
Meanwhile, those of you with the CMU TCP/IP, I'm sending out a collection
of my fixes to the TEKTCP mailing list. Tune in there (if it still works)
for the goods.
/Kevin Carosso kvc@engvax.scg.hac.com
Hughes Aircraft Co. kvc%engvax@oberon.usc.edu
Ps. Thanks to the people who relayed (second or third hand!) the clue
I needed to track this one down.