PIM Question

[Thomas Schmitt]

Hallo

I’m not sure what happens if I try a ping to multicast address. In picture below you can see the lab – is pretty simple – all Routers have ip multicast-routing active and all interfaces participate on PIM Routing in sparse-dense-mode. R2 and R3 are member from 224.1.1.1 group (Loopback 10.10.2.1 and 10.10.3.1). R3 and R4 are candidates for RP; R5 pings the 224.1.1.1 group.

Now I got 4 replays for 1 request from 2 host? (See picture below)How is it possible?

I sniffed the messages – but I do not clearly understand what PIM does – so I have some questions - can someone explain it to me?

• •1)      Why R5 sends first request before register message? If it doesn’t need register, why it does register with next message?
• •2)      Why it does send echo-request messages sometimes from 192.168.2.2 (f0/1 to R4) and sometimes from 1.1.5.1 Interface (Loopback).
• •3)      Why it sends register messages (after message 43) only for 1.1.5.1 Interface – multicast traffic is sent from 192.168.2.2 to.

[ashok_boin]

Hi,

Pls find answers for your questions...

• •1)      Why R5 sends first request before register message? If  it doesn’t need register, why it does register with next message?

This packet is originated through ICMP protocol so you were able to list in the beginning. In sparse mode, any source needs to register with RP.

• •2)       Why it does send echo-request messages sometimes from 192.168.2.2 (f0/1  to R4) and sometimes from 1.1.5.1 Interface (Loopback).

It generally checks through all interfaces to check for Multicast members of 224.1.1.1.

• •3)       Why it sends register messages (after message 43) only for 1.1.5.1  Interface – multicast traffic is sent from 192.168.2.2 to.

Not exactly sure about this. But, you can see PIM Register STOP messages from RP when the packets originated from 192.168.2.2 but not received the same message for 1.1.5.1.

Regards...

-Ashok.