On 04/09/12 12:00, Adam Vitkovsky wrote:
What I meant when I said IGMP register messages was actually IGMP membership
report message (commonly known as IGMP joins)
Yeah, I guessed that ;o)
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
Are you sure about this? In our environment, which is dual-routed HSRP,
we usually see the PIM DF be the *opposite* router to the IGMP querier,
because the election rules are different (PIM DF - higher IP; IGMP
querier - lower IP) and we're too lazy to add yet another line to the
SVI configs to set PIM/IGMP priority. For example:
# sh ip igmp vrf PROD int vl76
Vlan76 is up, line protocol is up
Internet address is x.x.x.254/24
IGMP is enabled on interface
Multicast Routing table PROD
Current IGMP host version is 2
Current IGMP router version is 2
...
Multicast routing is enabled on interface
Multicast TTL threshold is 0
Multicast designated router (DR) is x.x.x.254 (this system)
IGMP querying router is x.x.x.253
# sh ip pim vrf PROD int vl76 det
Vlan76 is up, line protocol is up
Internet address is x.x.x.254/24
Multicast switching: fast
Multicast packets in/out: 0/15871
Multicast TTL threshold: 0
PIM: enabled
PIM version: 2, mode: sparse
PIM DR: x.x.x.2541 (this system)
It doesn't seem to cause any problems, so we don't worry about it.
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