[Xorp-users] IGMP and Multicast question

Pavlin Radoslavov pavlin at ICSI.Berkeley.EDU
Tue Feb 5 20:29:34 PST 2008


> > 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.
> >
> The Juniper side is not our responsibility, so we can't make choices 
> for the people who are going to configure it. Between the Juniper and 
> our Xorp router, there is a satellite network, and cypher/decypher 
> devices, where it is necessary to configure security associations for 
> each flow you intend to transmit (unicast and multicast). That is the 
> main reason why we try not to have PIM signalling between the Juniper 
> and us. I asked the person in charge of the Juniper how it was going to 
> forward the multicast traffic, and he answered there was a simple 
> static configuration, the kind "all MC traffic from interface A shall 
> be directed to interface B". Does it make sense ?
> 
> To resolve my problem, which seems to be a RFC4605 (thanks Javier) test 
> case, couldn't I start two instances of Xorp on my Xorp router ?

The simple answer is no.

However, if Juniper forwards all multicast traffic to you, there is
a way to get it working:

1. Configure PIM-SM on XORP and configure one of its interfaces as a
   static RP for the whole 224.0.0.0/4 multicast address range.

2. Use the "alternative-subnet" configuration statement(s) for the
   interface/vif on the XORP box toward the Juniper.
   For example, "alternative subnet 10.0.0.0/8" will tell XORP to
   consider all multicast traffic from source address in the
   10.0.0.0/8 range appear like coming from a directly connected
   subnet, and typically traffic from directly connected subnets
   will be forwarded if there are downstream receivers.
   You might need to use more than one such statement to cover all
   possible sender addresses.

Regards,
Pavlin



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