Default Multicast Routing Configuration
This table describes the default multicast routing configuration for the device.
Table 20: Default Multicast Routing Configuration
Default Setting
Feature
Disabled on all interfaces.
Multicast routing
How to Configure Basic IP Multicast Routing
Configuring Basic IP Multicast Routing (CLI)
You must enable IP multicast routing and configure the PIM version and mode. After performing these tasks,
the software can then forward multicast packets, and the device can populate its multicast routing table.
You can configure an interface to be in PIM dense mode, sparse mode, or sparse-dense mode. The device
populates its multicast routing table and forwards multicast packets it receives from its directly connected
LANs according to the mode setting. You must enable PIM in one of these modes for an interface to perform
IP multicast routing.
Enabling PIM on an interface also enables IGMP operation on that interface.
If you enable PIM on multiple interfaces, when most of these interfaces are not on the outgoing interface
list, and IGMP snooping is disabled, the outgoing interface might not be able to sustain line rate for
multicast traffic because of the extra replication.
Note
In populating the multicast routing table, dense-mode interfaces are always added to the table. Sparse-mode
interfaces are added to the table only when periodic join messages are received from downstream devices or
when there is a directly connected member on the interface.
When forwarding from a LAN, sparse-mode operation occurs if there is a rendezvous point (RP) known for
the group. An RP acts as the meeting place for sources and receivers of multicast data. If an RP exists, the
packets are encapsulated and sent toward the RP. When no RP is known, the packet is flooded in a dense-mode
fashion. If the multicast traffic from a specific source is sufficient, the receiver
’
s first-hop router might send
join messages toward the source to build a source-based distribution tree.
By default, multicast routing is disabled, and there is no default mode setting.
This procedure is required.
IP Multicast Routing Configuration Guide, Cisco IOS XE Release 3SE (Catalyst 3650 Switches)
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Configuring IP Multicast Routing
Default Multicast Routing Configuration