Re: Multicast packets not being delivered to local host

Tech-Archive recommends: Repair Windows Errors & Optimize Windows Performance

From: Philip Restuccia (anonymous_at_discussions.microsoft.com)
Date: 05/21/04 

Date: Fri, 21 May 2004 12:06:08 -0700

     
     ----- Alan J. McFarlane wrote: -----
     
     Philip Restuccia <anonymous@discussions.microsoft.com> wrote:
> ----- Alan J. McFarlane wrote: -----
> Philip Restuccia <anonymous@discussions.microsoft.com> wrote:
> [...]
>> Does anyone have any ideas why this multicasting fails on
> these 2 > systems, but works fine on hundreds of others? One of
> the systems is > running Windows 2000 Professional Service Pack
> 2, the second is > running Service Pack 4. Any help would be
> greatly appreciated! >> Nothing definate comes to mind. Is there different third-party
> software on the machines, for instances third-party firewalls,
> virus checkers etc. They are notorious here!
>> First off, thanks for your reply, Alan!
>> No, these are all standard-issue systems as far as I know. There
> shouldn't be any significant differences between theses systems and
> all the others on which this same software does work.
>
     Standard-issue, except that some have SP2 and some SP4. Doesn't sound all
     that standard... :-)

Actually, one has SP2 and one has SP4 ... once they are distributed to the various
engineers, it is often up to the individual to keep it up to date. We do have a system
in place for automatic, centralized updates, but not everyone has their system
constantly connected to the local network (we have several telecommuters, for
example).

     
> Otherwise, maybe there's a difference with the default value for
> IP_MULTICAST_LOOP, give that a try. Try writing very simple
> client and server programs to allow troubleshooting the problem,
> to ensure its not something else that is provoking your software
> into this behaviour. Do you see the packets on the LAN if the
> TTL is one?
>> Actually, we explicitly do not use IP_MULTICAST_LOOP at all, since we
> don't want the sender of the ping to receive it.
>
     Yup. I was thinking about the behaviour that Unix has when I wrote that.
     IP_MULTICAST_LOOP there is a sender side option and it affects the "host"
     generally, see http://www.kohala.com/start/mcast.api.txt As you are on
     Windows and the sender and receiver are separate processes (and thus
     sockets) IP_MULTICAST_LOOP shouldn't affect you.

Right ... as I noted, this system works fine on literally thousands of other machines
(this is part of our production system, and we have quite a few customers using
it :-)

     
     [...]
     --
     Alan J. McFarlane
     http://homepage.ntlworld.com/alanjmcf/
     Please follow-up in the newsgroup for the benefit of all.
     
-- Philip Restuccuia

     

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