Digisol DG-GS4826S, Management Manual

Page: 603 / 1344

C
HAPTER
22 | Multicast Routing
Configuring PIM for IPv4
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u
PIM and IGMP proxy cannot be used at the same time. When an
interface is set to use PIM Dense mode or Sparse mode, IGMP proxy
cannot be enabled on any interface of the device (see "Configuring
IGMP Snooping and Query Parameters" on page 427 ). Also, when IGMP
proxy is enabled on an interface, PIM cannot be enabled on any
interface.
PIM-DM
u
PIM-DM functions similar to DVMRP by periodically flooding the network
with traffic from any active multicast server. It also uses IGMP to
determine the presence of multicast group members. The main
difference, is that it uses the router’s unicast routing table to determine
if the interface through which a packet is received provides the shortest
path back to the source.
u
Dense-mode interfaces are subject to multicast flooding by default, and
are only removed from the multicast routing table when the router
determines that there are no group members or downstream routers,
or when a prune message is received from a downstream router.
PIM-SM
u
A PIM-SM interface is used to forward multicast traffic only if a join
message is received from a downstream router or if group members
are directly connected to the interface. When routers want to receive a
multicast flow, they periodically send join messages to the RP, and are
subsequently added to the shared path for the specified flow back up to
the RP. If routers want to join the source path up through the SPT, they
periodically send join messages toward the source. They also send
prune messages toward the RP to prune the shared path once they
have connected to the source through the SPT, or if there are no longer
any group members connected to the interface.
P
ARAMETERS
These parameters are displayed in the web interface:
Common Attributes
u
VLAN – Layer 3 VLAN interface. (Range: 1-4093)
u
Mode – PIM routing mode. (Options: Dense, Sparse, None)
u
IP Address – Primary IP address assigned to the selected VLAN.
u
Hello Holdtime – Sets the interval to wait for hello messages from a
neighboring PIM router before declaring it dead. Note that the hello
holdtime should be greater than or equal to the value of Hello Interval,
otherwise it will be automatically set to 3.5 x the Hello Interval.
(Range: 1-65535 seconds; Default: 105 seconds, or 3.5 times the hello
interval if set)
u
Hello Interval – Sets the frequency at which PIM hello messages are
transmitted out on all interfaces. (Range: 1-65535 seconds;
Default: 30 seconds)