Digisol DG-GS4826S, Management Manual

Page: 609 / 1344

C
HAPTER
22 | Multicast Routing
Configuring PIM for IPv4
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u
Register Source – Configures the IP source address of a register
message to an address other than the outgoing interface address of the
DR that leads back toward the RP. (Range: VLAN 1-4094; Default: The
IP address of the DR’s outgoing interface that leads back to the RP)
When the source address of a register message is filtered by
intermediate network devices, or is not a uniquely routed address to
which the RP can send packets, the replies sent from the RP to the
source address will fail to reach the DR, resulting in PIM-SM protocol
failures. This type of problem can be overcome by manually configuring
the source address of register messages to an interface that leads back
to the RP.
u
SPT Threshold – Prevents the last-hop PIM-SM router from switching
to Shortest Path Source Tree (SPT) mode. (Options: Infinity, Reset;
Default: Reset, or use the SPT)
The default path for packets from a multicast source to a receiver is
through the RP. However, the path through the RP is not always the
shortest path. Therefore, the router uses the RP to forward only the
first packet from a new multicast group to its receivers. Afterwards, it
calculates the shortest path tree (SPT) directly between the receiver
and source, and then uses the SPT to send all subsequent packets from
the source to the receiver instead of using the shared tree. Note that
when the SPT threshold is not set by this command, the PIM leaf router
will join the shortest path tree immediately after receiving the first
packet from a new source.
Enable the SPT threshold to force the router to use the shared tree for
all multicast groups, or just for the specified multicast groups.
u
Group Address – An IP multicast group address. If a group address is
not specified, the shared tree is used for all multicast groups.
u
Group Mask – Subnet mask that is used for the group address.
W
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I
NTERFACE
To configure global settings for PIM-SM:
1. Click Multicast, Multicast Routing, SM.
2. Select Configure Global from the Step list.
3.
Set the register rate limit and source of register messages if required.
Also specify any multicast groups which must be routed across the
shared tree, instead of switching over to the SPT.
4. Click Apply.