Specifications
1-24
Cisco MWR 2941 Mobile Wireless Edge Router Software Configuration Guide, Release 12.2(33)MRB
OL-21227-02
Chapter 1 Cisco MWR 2941 Router Overview
Features
PIM Modes
Cisco IOS defines the following PIM modes:
• PIM Dense Mode—Uses a push model to flood multicast traffic to every corner of the network. This
push model is a method for delivering data to the receivers without the receivers requesting the data.
This method is efficient in certain deployments in which there are active receivers on every subnet
in the network. Dense mode is not supported in Release 12.2(33)MRB.
• PIM Sparse Mode—Uses a pull model to deliver multicast traffic. Only network segments with
active receivers that have explicitly requested the data will receive the traffic. PIM sparse mode is
supported in Release 12.2(33)MRB.
• Sparse-Dense Mode—PIM runs sparse and dense mode according to the group mode; the interface
is treated as dense mode if the group is in dense mode; the interface is treated in sparse mode if the
group is in sparse mode. Sparse-dense mode is supported in Release 12.2(33)MRB.
• Bidirectional PIM—Traffic is routed only along a bidirectional shared tree that is rooted at the RP
for the group. In bidir-PIM, the IP address of the RP acts as the key to having all routers establish a
loop-free spanning tree topology rooted in that IP address. Bidirectional PIM is not supported in
Release 12.2(33)MRB.
For more information about PIM modes, see the Cisco IOS IP Multicast Configuration Guide, Release
12.2SR.
Multicast Group Modes
In PIM, packet traffic for a multicast group is routed according to the rules of the mode configured for
that multicast group. Cisco IOS supports four modes for a multicast group:
• PIM Bidirectional mode—Traffic is routed only along a bidirectional shared tree that is rooted at
the rendezvous point (RP) for the group.
• PIM Sparse mode—Uses a unidirectional shared tree whose root node is called the rendezvous point
(RP).
• PIM Dense mode—Dense mode operates using the broadcast (flood) and prune model.
• PIM Source Specific Multicast (SSM) mode—Datagram traffic is forwarded to receivers from only
those multicast sources that the receivers have explicitly joined.
The MWR 2941 supports PIM Sparse mode and PIM SSM mode.
Sparse Mode
Sparse mode operation centers around a single unidirectional shared tree whose root node is called the
rendezvous point (RP). Sources must register with the RP to get their multicast traffic to flow down the
shared tree by way of the RP. This registration process actually triggers a shortest path tree (SPT) Join
by the RP toward the source when there are active receivers for the group in the network.
A sparse mode group uses the explicit join model of interaction. Receiver hosts join a group at a
rendezvous point (RP). Different groups can have different RPs.
Multicast traffic packets flow down the shared tree to only those receivers that have explicitly asked to
receive the traffic.
Note The Cisco MWR 2941 supports sparse mode with a single static Rendezvous Point.