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From: ted@blia.UUCP (Ted Marshall)
Newsgroups: mod.computers.vax
Subject: submission for mod.computers.vax
Message-ID: <8611260030.AA27067@blia.BLI>
Date: Tue, 25-Nov-86 19:30:39 EST
Article-I.D.: blia.8611260030.AA27067
Posted: Tue Nov 25 19:30:39 1986
Date-Received: Wed, 26-Nov-86 20:51:12 EST
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Subject: Re: Re:  Ethernet promiscuious mode (VAX/VMS)
Newsgroups: mod.computers.vax
Summary: small correction
References: <8611241538.AA10222@ucbvax.Berkeley.EDU>

In article <8611241538.AA10222@ucbvax.Berkeley.EDU>, LEICHTER-JERRY@YALE.ARPA writes:
> WARNING:  Be aware of one restriction, which may not be obvious when you first
> read the documentation:  An Ethernet interface in promiscuous mode cannot be
> shared.  In particular, you will not be able to run DECnet through the device
> while you are using it in this mode.

This is not quite true in my experience. There can only be one port on
a DxxxA set to promiscuious mode at any time. "Normal" ports can
co-exist with the promiscuious port. However now, instead of the
hardware doing incoming address filtering, the hardware must give EVERY
message on the ethernet to the driver which then does the address
filtering for the normal ports. The upshot of this is that if you have
a slow VAX or ethernet interface (i.e. the DEC DEQNA) and a busy
ethernet, the driver will miss so many messages that most protocols
will fail.

I wrote an ethernet traffic monitor using promiscuious mode. While
running it on our 11/750, DECnet worked ok most of the time. If I tried
it on our u-VAX II, all of the DECnet links would break every time.