Pim-Dm Configuration - 3Com 8807 Configuration Manual

456 C 43: PIM-DM C
HAPTER

PIM-DM Configuration

ONFIGURATION
forwarding. The unicast routing information as path judgment can come from any
unicast routing protocol independent of any specified unicast routing protocol
such as the routing information learned by RIP and OSPF
Assert mechanism
As shown in the following figure, both routers A and B on the LAN have their own
receiving paths to multicast source S. In this case, when they receive a multicast
packet sent from multicast source S, they will both forward the packet to the LAN.
Multicast Router C at the downstream node will receive two copies of the same
multicast packet.
Figure 110 Assert mechanism diagram
Router A
When they detect such a case, routers need to select a unique sender by using the
assert mechanism. Routers will send Assert packets to select the best path. If two
or more than two paths have the same priority and metric, the path with a higher
IP address will be the upstream neighbor of the (S, G) entry, which is responsible
for forwarding the (S, G) multicast packet.
n
Currently assert mechanism is not available on the 3Com Switch 8800 Family
Series Routing Switches.
Graft
When the pruned downstream node needs to be restored to the forwarding state,
the node will send a graft packet to inform the upstream node.
1 PIM-DM basic configuration includes:
Enabling multicast
■
Enabling PIM-DM
■
2 PIM-DM advanced configuration includes:
Configuring the time interval for ports to send Hello packets
■
Entering the PIM view
■
Configuring filtering of multicast source/group
■
Configuring filtering of PIM neighbor
■
Multicast packets forwarded by the
upstream node
Router C
Router B
Receiver