Yenya's World

Thu, 24 May 2007

Playing With Multicast

We have our hot-spare router back from repair, and it has been working for a week without crash so far. So I have finally got a chance to play with new features of our network without having to fear that I lose the whole network in case of a misconfiguration. The first thing which was long overdue was native multicast (the second one being native IPv6 on all our networks).

It seems that the basic multicast sending and receiving data works - the following example uses VideoLan Client:

stream-server$ vlc -vvv MyFavouriteAnime.avi --sout udp: --ttl 2
stream-client$ vlc -vvv udp:@

However, it seems only some of the multicast-able hosts on my network can answer to the ping -t 2 -c 2 So far I have not figured out what to do in order to make the remaining hosts answer the above ping.

The Linux multicast routing, on the other hand, is a very sorrowful area. The HOWTOs are many years old and obsolete, the routing programs like mrouted or pimd are not being worked on anymore. The mailing lists and discussion boards are full of questions without answers, like this one at KernelTrap. For example, on my router the /proc/sys/net/ipv4/conf/*/mc_forwarding files are read-only, and the /proc/net/ip_mr_cache file is empty no matter what I do.

I have yet to try some more tricks mentioned in the above KernelTrap thread. But nevertheless, my dear lazyweb, does anyone have a working Linux-based multicast router?

Section: /computers (RSS feed) | Permanent link | 2 writebacks

2 replies for this story:

Vasek Stodulka wrote:

I don't have a multicast router, but - are you sure, that IPv6 multicast uses the ancient IPv4 multicast interface? I remember these options from 2.2 kernels, I have never turned them on...

tomfi wrote: Ping responses

I've tried the ping to all ( in our network, and guess ... only ovises in provider's network responded :) .... I see you want to route multicast traffic... multicast able router must respond on address ... try your router ;) Host must reply on only when it needs multicasts ... not all time (I think)

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