PIM-DM

PIM- Dense Mode:

• used in a situation:
• networks where many multicast clients are tightly spaced together in small networks.

PIM: Protocol Independent Multicast

• PIM is used for router to router communication.
• PIM depend upon the unicast routing protocols for topology information.
• Multicast groups can be either sparse or dense.
• Multicast interfaces are configured as either sparse or dense or both.
• PIMv2 hello message: 30sec
• on PIM enabled interfaces.
• PIMv2 hold time value: 90sec
• PIMv2 uses protocol 103 & reserved multicast address 224.0.0.13
• PIM mode only determine how traffic is send from an interface, not how it recieved.
• DR Router: single router send  IGMP host-query messages to host group membership
• Highest ip number will be DR
• Assert Forwarder: 
• one router will be elected & responsible for forwarding multicast traffic.
• AS election:
• admin distance to the source
• lowest metric to the source
• if tie, highest ip address