Manual

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Москва, Новозаводская ул., 18, стр. 1
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3. RPF examination
Adopting RPF examination, PIM-DM establishes a multicast forwarding tree initiating from data
source, using existing unicast routing table. When a multicast packet arrives, the router will
determine the correctness of its coming path first. If the arrival interface is the interface
connected to multicast source indicated by unicast routing, then this multicast packet is
considered to be from the correct path; otherwise the multicast packet will be discarded as
redundant message. The unicast routing message used as path judgment can root in any
Unicast Routing Protocol, such as messages found by RIP, OSPF, etc. It doesn’t rely on any
specific unicast routing protocol.
4. Assert Mechanism
If two multicast router A and B in the same LAN segment have their own receiving paths to
multicast source S, they will respectively forward multicast data packet to LAN after receiving
the packet from multicast source S. Then downstream nodes multicast router C will receive
two multicast packets that are exactly the same. Once router detects such circumstance, a
unique forwarder will be selected through “assert” mechanism. The optimized forwarding path
is selected through “assert” packet. If the priority and costs of two or more than two paths are
same, the node with a larger IP address will be selected as the upstream neighbor of item (S,
G), which will be responsible for forwarding the (S, G) multicast packet.
5. Graft
When the pruned downstream node needs to recover to forwarding status, this node uses
Graft Message to notify upstream nodes to resume multicast data forwarding.
29.1.2 PIM-DM6 Configuration Task List
Enable PIM-DM (Required)
Configure static multicast routing entries (Optional)
Configure additional PIM-DM parameters (Optional)
Configure parameters for PIM-DM interfaces
Configure the interval for PIM-DM hello messages
Configure the interval for PIM-DM state-refresh messages
Configure the boundary interfaces
Configure the management boundary
Disable PIM-DM protocol
1. Enable the PIM-DM protocol
On QTECH series switches, PIM-DM can be enabled through two steps. Firstly PIM multicast
routing should be enabled in global configuration mode, then PIM-DM should be configured for
the specific interfaces.