multicast problem in Fram-relay

[yi-chen]

hub and spoke

r1

| |

r2 r3

the frame-relay interface of the three routers are in one subnet

frame-relay map with broadcast

pim dense-mode

r2's ethernet interface join one multicast group:239.1.1.1

r1 can ping this multicast address,but r3 can not.

what's the problem?

[Georg Pauwen]

Can you post the configs ?

[yi-chen]

r1(hub)

int s0

ip add 10.10.1.1 255.255.0.0

encapsulation fram-relay

ip pim dense-mode

r2(spoke)

int s0

ip add 10.10.1.2 255.255.0.0

ip pim dense-mode

encapsulation frame-relay

int e0

ip add 10.100.1.2 255.255.255.0

ip pim dense-mode

ip igmp join-group 239.1.1.1

r3(spoke)

int s0

ip add 10.10.1.3 255.255.0.0

encapsulation fram-relay

ip pim dense-mode

[drogell]

Since this is a hub and spoke you would have yo add the ip pim nbma-mode

[yi-chen]

it doesn't work

[ikraehenmann]

When a multicast packet arrives on r1, it creates (*,G) state containing all interfaces that possibliy need to forward traffic (PIM neighbours, IGMP groups). To actually forward traffic, (S,G) state is set up. The incoming interface is the one, where the packet is received from, the OIL contains the rest of the interfaces from (*,G).

Sinde the frame relay interface is the incoming interface, your packet is not forwarded out of this interface again and therefore does not get from r2 to r3.

NBMA mode does not help either, because it can only collect the additional information form SM joins

The most effective solution is to use subinterfaces.