Technical Note: Why multicast traffic to multiple paths to same destination do not use all interfaces in dense mode
Description
Solution
In Multicast dense mode is expected flooding of traffic on all related interfaces expect those to same destination.
Solution
The reason is mentioned on RFC 3973 as follows:
"(S,G) State
For every source/group pair (S,G), a router stores the following state:
(S,G) state:
For each interface:
Local Membership:
State: One of {"NoInfo", "Include"}
PIM (S,G) Prune State:
State: One of {"NoInfo" (NI), "Pruned" (P), "PrunePending" (PP)}
Prune Pending Timer (PPT)
Prune Timer (PT)
(S,G) Assert Winner State:
State: One of {"NoInfo" (NI), "I lost Assert" (L), "I won Assert" (W)}
Assert Timer (AT)
Assert winner's IP Address
Assert winner's Assert Metric"
There are three states:
NoInfo (NI)
This router has no (S,G) Assert state on interface I.
I am Assert Winner (W)
This router has won an (S,G) Assert on interface I. It is now responsible for forwarding traffic from S destined for G via interface I.
I am Assert Loser (L)
This router has lost an (S,G) Assert on interface I. It must not forward packets from S destined for G onto interface I."
After initial flooding only one path to same destination will be elected as "Winner"
"(S,G) State
For every source/group pair (S,G), a router stores the following state:
(S,G) state:
For each interface:
Local Membership:
State: One of {"NoInfo", "Include"}
PIM (S,G) Prune State:
State: One of {"NoInfo" (NI), "Pruned" (P), "PrunePending" (PP)}
Prune Pending Timer (PPT)
Prune Timer (PT)
(S,G) Assert Winner State:
State: One of {"NoInfo" (NI), "I lost Assert" (L), "I won Assert" (W)}
Assert Timer (AT)
Assert winner's IP Address
Assert winner's Assert Metric"
There are three states:
NoInfo (NI)
This router has no (S,G) Assert state on interface I.
I am Assert Winner (W)
This router has won an (S,G) Assert on interface I. It is now responsible for forwarding traffic from S destined for G via interface I.
I am Assert Loser (L)
This router has lost an (S,G) Assert on interface I. It must not forward packets from S destined for G onto interface I."
After initial flooding only one path to same destination will be elected as "Winner"