Cisco Systems 78-11741-02 Wireless Office Headset User Manual


 
Configuring IP Multicast Routing
Enabling PIM on an Interface
IPC-405
Cisco IOS IP Configuration Guide
Configuring PIM Dense Mode State Refresh
If you have PIM dense mode (PIM-DM) enabled on a router interface, the PIM Dense Mode State
Refresh feature is enabled by default.
PIM-DM builds source-based multicast distribution trees that operate on a “flood and prune” principle.
Multicast packets from a source are flooded to all areas of a PIM-DM network. PIM routers that receive
multicast packets and have no directly connected multicast group members or PIM neighbors send a
prune message back up the source-based distribution tree toward the source of the packets. As a result,
subsequent multicast packets are not flooded to pruned branches of the distribution tree. However, the
pruned state in PIM-DM times out approximately every 3 minutes and the entire PIM-DM network is
reflooded with multicast packets and prune messages. This reflooding of unwanted traffic throughout the
PIM-DM network consumes network bandwidth.
The PIM Dense Mode State Refresh feature keeps the pruned state in PIM-DM from timing out by
periodically forwarding a control message down the source-based distribution tree. The control message
refreshes the prune state on the outgoing interfaces of each router in the distribution tree.
This feature also enables PIM routers in a PIM-DM multicast network to recognize topology changes
(sources joining or leaving a multicast group) before the default 3-minute state refresh timeout period
expires.
By default, all PIM routers that are running a Cisco IOS software release that supports the PIM Dense
Mode State Refresh feature automatically process and forward state refresh control messages. To disable
the processing and forwarding of state refresh control messages on a PIM router, use the ip pim
state-refresh disable global configuration command.
To configure the origination of the control messages on a PIM router, use the following commands
beginning in global configuration mode:
Note The origination interval for the state refresh control message must be the same for all PIM routers on
the same LAN. Specifically, the same origination interval must be configured on each router interface
that is directly connected to the LAN.
See the “PIM Dense Mode State Refresh Example” section later in this chapter for an example of how
to configure the PIM Dense Mode State Refresh feature.
Command Purpose
Router(config-if)# ip pim sparse-dense-mode
Enables PIM to operate in sparse or dense mode, depending on
the group.
Command Purpose
Step 1
Router(config)# interface type number
Specifies an interface and places the router in interface
configuration mode.
Step 2
Router(config-if)# ip pim state-refresh
origination-interval [interval]
Configures the origination of the PIM Dense Mode State Refresh
control message. Optionally, you can configure the number of
seconds between control messages by using the interval
argument. The default interval is 60 seconds. The interval range
is from 4 to 100 seconds.