[Xorp-users] IGMP and Multicast question

[Javier Fernandez-Sanguino]

2008/2/5, expo01 at free.fr <expo01 at free.fr>:
> Hi,
>
> We are trying to make the following work, as a test platform for now, but then
> it will be needed in a real case operation :
>
> mcast source-------Linux smcroute---------LinuxXORP-------mcast receiver
>           ^                             ^        ^       ^
>           |                             |        |       |
>       192.168.1.1                      eth0     eth1     192.168.3.4
>                                   192.168.2.3  192.168.3.3

Linux smcroute and LinuxXorp are different systems, right?

Question: why don't you enable IGMP on the eth0 interface?

I don't see how you can make this work, AFAIK Xorp cannot act as an
IGMP proxy (RFC4605?) and if you are working with two routers you need
to have PIM in both sides (i.e. in the Linux smcroute and LinuxXorp).

Actually, you are not simulating properly the Juniper case by just
adding a Linux system with smcroute. You need to have a PIM-enabled
daemon in that side, to simulate multicast routing amongst routers.

> Our understanding of what should occur is probably wrong, but we thought that
> the IGMP report received from the MC receiver should be enough for the XORP
> router to have the necessary information to be able to forward the stream
> received on eth0 to eth1. What is not correct in this assumption ?

No, from my limited understanding (I'm not a multicast guru, but hey)
the Xorp router has to "find" which multicast routers are available
(through PIM) and then, when it sees, the IGMP repo from a MC receiver
on its side it will "subscribe" to the multicast group with its main
multicast router. In your environment there is only one multicast
router (i.e. Xorp) so it does not know who to contact to get the group
 230.1.1.1 requested by the client.

That being said, I'm not sure if it will work if you add eth0 to the
IGMP definition, as smcroute will just forward (if properly
configured) the multicast traffic from the server "as is". Did you try
that?


Regards

Javier