[AG-TECH] IP Multicast address patterns??
Thomas D. Uram
turam at mcs.anl.gov
Tue Sep 6 15:09:58 CDT 2005
See comments inline...
Many Ayromlou wrote:
> I just had a discussion with some of our Network guys and they have
> asked me to see if there is a possible way to give them a list of IP
> multicast addresses that AG venueservers use. They are trying to modify
> the rendevous point on our router based on Multicast addresse ranges,
> since a lot of these new "Ghost" like applications use multicast to
> mirror disks across networks with wrong ttl's and hard coded IP
> addresses that are not in the admin range.
> Anyways.....my question for the Venueserver Gurus :-).....Is there a
> pattern to the way VV Servers allocate addresses??
By default, mcast addresses are allocated in the range 126.96.36.199/17, which you can see
in the MulticastAddressAllocator.py code. The Argonne venue servers use these defaults.
You could query this range for a particular server using VenueServerIW.GetBaseAddress and
VenueServerIW.GetAddressMask, but you would need to be an admin on the server for the
calls to succeed.
.....I've noticed a
> lot of 224.x.x.x and 233.x.x.x and I've also seen the ncsa page that
> keeps track of some of them (https://agschedule.ncsa.uiuc.edu:443/
> venues.asp). Or better yet is there some way of querying the info from
> the VV Server through some simple means?
You can query a venue programmatically for its multicast addresses using the
VenueIW.GetStreams method. I put together a script that does this here:
Given a venue address, it will print the mcast addresses assigned to the venue. You could
use this tool to crawl for mcast addresses; let me know if you're interested, since there
are some authorization hurdles in the way of such crawling.
I really don't want to
> dedicate one of my students to sit there and click every single Venue
> on all the servers out there to make a list.
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