All things related to multicast

[Pekka Savola <>]

On Fri, 13 Jul 2007, Ying Zhang wrote:
> V2 queries from router, and router sees IGMP V3 membership reports from host. 
> The host is running Fedora 7 and VLC 0.8.6c. I then changed the router to run 
> IGMP v3 on that interface. I then saw queries and reports in V3, but still 
> didn't get the  SAP streams.
>
> Also I am curious, if VLC sends out IGMP v3 reports, should it then ask user 
> to put in a source address? I didn't see where to do it on VLC. Did I miss 
> anything?
>
> Any suggestions are appreciated.

I've seen this behaviour in two cases:

 1) the host has a firewall which prevents it from seeing IGMPv2 reports. 
For example, default RHEL and Fedora iptables rules do this.

 2) host's IGMPv3 implementation is buggy and revert doesn't work, or it 
ceases to work after some time.  I've seen this on RHEL3 kernels AFAIR.

Pekka

> ----- Original Message ----- From: "Stig Venaas" 
> <>
> To: "Ying Zhang" 
> <>
> Cc: "Bob Riddle" <>; "Marshall Eubanks" <>; 
> "Nicholas J Humfrey" <>; "wg-multicast" 
> <>
> Sent: Friday, July 06, 2007 3:50 AM
> Subject: Re: VLC + Vista Multicast Issues
>
>
> > Ying Zhang wrote:
> > > I've seen similar problem on Unix box running VLC. It sends IGMP V3 
> > > messages and didn't revert to V2, couldn't get SAP announcement. Just 
> > > wondering if anyone saw this?
> >
> > Not personally. I've encountered some strange situations related to
> > IGMP myself. There appear to be issues with both some router and some
> > host implementations. And then there have been cases where the switch
> > for some reason didn't forward the IGMP messages.
> >
> > I guess it could be useful to try to document such issues. But it would
> > be good to understand better what is going on. For instance, try to
> > check that the host indeed receives the IGMPv2 queries, and whether it
> > sends IGMPv2, IGMPv3 or no reports,
> >
> > Stig