Oh yes I'm sorry for confusion thank you Phil for pointing that out What I meant when I said IGMP register messages was actually IGMP membership report message (commonly known as IGMP joins) IGMP membership report messages from local subnet are translated by the designated forwarder into PIM joins and sent up the shared or source-tree depending on whether the source for the particular m-cast group is known or not
Also to clarify IGMP querier is the router elected by PIM(igmp ver2/3) as a router that sends IGMP queries for the local subnet PIM designated forwarder is elected by PIM as a router responsible for forwarding m-cast traffic down/from the local subnet Since IGMPver2 PIM process is responsible for election of both function -so they always reside on the same router > PIM registers are sent for multicast *sources*. They're sent by the PIM designated forwarder towards the RP and flooded down the (*,g) tree so that (s,g) joins can be triggered. They are re-sent periodically to refresh state on the RP. For more details During the PIM register process the PIM designated forwarder (first-hop router -router that has the source on the directly connected subnet) encapsulates the m-cast packet sent by source host into a unicast register message that is sent as unicast to the RP RP de-capsulates the register msg and learns the multicast group and the particular source and can build the shared tree towards the first-hop router as designated by the (*,g) state in all the routers After the shared-tree is built from the RP all the way to the first-hop router -the first hop router will than start sending the m-cast traffic up the shared tree Now the RP receives the m-cast traffic twice -via the PIM register messages and via the shared tree RP than sends register stop messages towards the first hop router -informing it that it no longer needs to send the register messages This whole process can span over a network consisting of many m-cast routers adam -----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of Phil Mayers Sent: Tuesday, September 04, 2012 11:01 AM To: [email protected] Subject: Re: [c-nsp] MSDP and my limited knowledge question On 09/04/2012 09:12 AM, Adam Vitkovsky wrote: > As Paul said IGMP register messages are supposed to be handled by the > router elected as designated querier for the local subnet Though AFAIK > IGMP register process is only used by the m-cast receivers not the > sources For clarity, because I think you typo-ed a couple of things there: PIM registers are sent for multicast *sources*. They're sent by the PIM designated forwarder towards the RP and flooded down the (*,g) tree so that (s,g) joins can be triggered. They are re-sent periodically to refresh state on the RP. IGMP joins are sent by multicast *receivers*. They trigger (*,g) joins [or (s,g) joins for IGMPv3 SSM] towards the RP. When a new source appears on the (*,g) tree, the routers are triggered to do an (s,g) join. MSDP essentially "echos" PIM register state between PIM RPs, allowing separate PIM networks to be connected without (*,g) flooding on the interconnect link, which wouldn't scale well. The OPs problem is that he's trying to source multicast traffic from an IP on his Linux box that isn't a "connected" route on the c4900. Thus, the c4900 isn't the PIM DF, so doesn't send the PIM register or MSDP advertisments. That doesn't (can't) work, I believe. AFAIK there's no "PIM DF proxy" IOS feature, though I can see situations in which it would be useful. _______________________________________________ cisco-nsp mailing list [email protected] https://puck.nether.net/mailman/listinfo/cisco-nsp archive at http://puck.nether.net/pipermail/cisco-nsp/ _______________________________________________ cisco-nsp mailing list [email protected] https://puck.nether.net/mailman/listinfo/cisco-nsp archive at http://puck.nether.net/pipermail/cisco-nsp/
