[Xorp-users] IGMP and Multicast question

[Pavlin Radoslavov]

> > > 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?
> Yes, indeed. We used smcroute only for the test, because it is quick to
> configure.
> >
> > Question: why don't you enable IGMP on the eth0 interface?
> In my understanding, activating an interface for igmp in Xorp means "listen for
> potential receivers on this interface". And I know we have receivers only on
> eth1. Am I wrong ? By the way, in a first configuration I in fact had configured
> eth0 for igmp also, with no difference in behaviour.
> >
> > 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.
> See below my comments about a "two PIM routers" configuration.
> 
> > > 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?
> Yes, we tried and saw no difference. We also tried to have a Xorp Pim daemon
> running instead of  smcroute, and it did work, the receiver had the MC flow
> directed to him (it ?), but in the real world case, there will not be a PIM
> router on the Juniper (AFAIK as of today).

Juniper has PIM-SM so is there any reason not to configure/use it?
If Juniper won't be running PIM how are you going to get that box
forward the multicast traffic? Are you planning to have it running
IGMP proxy?
If this is the case then XORP needs to run PIM-SM with little
special configuration. I can provide that info to you once I
know what are you going to do on the Juniper side.

Regards,
Pavlin