Henry's Points

There are two interesting topics in IP Multicast network to solve problem on Frame Relay network. Frame relay network is non-broadcast media access network type. However, it can perform “pseudo-broadcast” and performed at router’s CPU level. Frame relay network is also hub-spoke network type. So, here are two problems.

1. Since IP multicast is perform RPF calcuation, how one spoke send multicast traffic to another spoke?
2. If multicast source is on the top of Hub, since OIL (outgoing interface list) is only one serial interface, how the traffic is going to only the spoke which required multicast traffic, in stead of all spokes?

ip nbma-mode is one of the solutions. First, NBMA mode is ONLY working on PIM sparse mode. Second, if one serial interface enable NBMA mode, it automatically change OIL to the spoke IP address, not outgoing interface anymore. Thus, The traffic can only go to that spoke.

GRE tunnel is another way to solve spoke traffic to another spoke.

We can see from diagram above that, R4 is MA (Mapping Agent), R4 will advertise RP information to all 224.0.1.40 by using PIM dense mode. Remeber, Auto-RP is communicated by using PIM Dense Mode. RP will send advertised to 224.0.1.39, which is listened by MA. Then, MA send advertisement to all 224.0.1.40. The traffic will never go to R1 even though NBMA mode is enabled on R5. So, we need create a GRE tunnel between R4 and R1.

R4

interface tunnnel 0

tunnel source loopback 0

tunnel destination 150.1.1.1

ip unnumber loopback 0

ip pim sparse-mode

R1

interface tunnel 0

tunnel source loopback 0

tunnel destination 150.1.4.4

ip unnumber loopback 0

ip pim sparse-mode

However, when show ip pim rp mapping on R1, there is no RP shown. This is because RPF failure. When we show ip route 150.1.4.4 on R1, it point to serial interface, but Mapping Agenet is learned from tunnel interface. So, we need add a static mroute on the global.

ip mroute 150.1.4.4 255.255.255.255 tunnel 0

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