3Com Switch 4800G 24-Port Configuration Manual page 642

642 C 47: PIM C
HAPTER ONFIGURATION
c
Enabling State Refresh
Configuring State
Refresh Parameters
CAUTION:
All the interfaces of the same router must work in the same PIM mode.
■
PIM-DM cannot be used for multicast groups in the SSM group grange.
■
An interface without the state refresh capability cannot forward state refresh
messages.
Follow these steps to enable the state refresh capability:
To do...
Enter system view
Enter interface view
Enable state refresh
To avoid the resource-consuming reflooding of unwanted traffic caused by
timeout of pruned interfaces, the router directly connected with the multicast
source periodically sends an (S, G) state refresh message, which is forwarded hop
by hop along the initial multicast flooding path of the PIM-DM domain, to refresh
the prune timer state of all the routers on the path.
A router may receive multiple state refresh messages within a short time, of which
some may be duplicated messages. To keep a router from receiving such
duplicated messages, you can configure the time the router must wait before
receiving the next state refresh message. If a new state refresh message is received
within the waiting time, the router will discard it; if this timer times out, the router
will accept a new state refresh message, refresh its own PIM state, and reset the
waiting timer.
The TTL value of a state refresh message decrements by 1 whenever it passes a
router before it is forwarded to the downstream node until the TTL value comes
down to 0. In a small network, a state refresh message may cycle in the network.
To effectively control the propagation scope of state refresh messages, you need
to configure an appropriate TTL value based on the network size.
Follow these steps to configure state refresh parameters:
To do...
Enter system view
Enter PIM view
Configure the interval
between state refresh
messages
Configure the time to wait
before receiving a new state
refresh message
Configure the TTL value of
state refresh messages
Use the command...
system-view
interface interface-type
interface-number
pim state-refresh-capable
Use the command...
system-view
pim
state-refresh-interval
interval
state-refresh-rate-limit
interval
state-refresh-ttl ttl-value
Remarks
-
-
Optional
Enabled by default
Remarks
-
-
Optional
60 seconds by default
Optional
30 seconds by default
Optional
255 by default