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Re: How to pick a Site-Local Scope multi cast address

  • From: Marshall Eubanks
  • Date: Sat Dec 09 15:41:08 2006


I think that pretty much everything John Kristoff said was spot on, especially to thank you for asking.

Unfortunately, there is no general method for doing this except to use your GLOP address, if you have one, and that is not really appropriate for site-local work. Madcap and MZAP were implemented into Windows, but I have never heard of them being used.

If you look at
it says that Site-Local Scope [Meyer,RFC2365]
should be used for site local scope, but I know that that is not really followed much either.

So, my advice is

- pick something at random from 239.255/16
- let us know what it is
- give the user a config file or some other means to change it if they have too.

I would be glad to collect and maintain a list of site-local multicast addresses, but I have no illusions that
such a list would be complete. It would be worth doing, however.

If you really feel that this is something where there will be millions deployed, contact me offlist and we
can discuss getting an address from IANA.

Hope this helped, and, again, thank you for asking.

Marshall Eubanks

On Dec 8, 2006, at 10:54 AM, Dave Raskin wrote:

Hello, I have been directed to this list by IANA when I asked the
following question:

I am researching ways of device/machine discovery on the
network. This
is similar to the Discovery phase of UPnP devices, which uses the SSDP

I have researched far enough to know that my best bet for UDP
multicast address group is the Site-Local Scope address range of

SSDP and UPnP protocols use the address

My question is this:

How do I pick a group address within this range and not have a
chance of colliding with some other application on the network already
using the group address I just picked?

Do I just randomly pick an address in that range and hope for
the best? I am running on Windows and cannot assume that there is a
MADCAP server available.

Thanks in advance!

Dave Raskin
Rimage Corporation