User Manual UMN:CLI
V5808
413
9.2 Multicast Functions
The V5808 provides various multicast functions including Layer 2 multicast forwarding,
which allow you to achieve the fully effective and flexible multicast deployment.
9.2.1 Multicast Forwarding Database
Internally, the V5808 forwards the multicast traffic referred to the multicast forwarding
database (McFDB). The McFDB maintains multicast forwarding entries collected from
multicast protocols and features, such as PIM, IGMP, etc.
The McFDB has the same behavior as the Layer 2 FDB. When certain multicast traffic
comes to a port, the switch looks for the forwarding information (the forwarding entry) for
the traffic in the McFDB. If the McFDB has the information for the traffic, the switch
forwards it to the proper ports. If the McFDB does not have the information for the traffic,
the switch learns the information on the McFDB, and then floods it to all ports. If the
information is not referred to forward another multicast traffic during the given aging time,
it is aged out from the McFDB.
9.2.1.1 Blocking Unknown Multicast Traffic
When certain multicast traffic comes to a port and the McFDB has no forwarding
information for the traffic, the multicast traffic is flooded to all ports by default. You can
configure the switch not to flood unknown multicast traffic.
To configure the switch to discard unknown multicast traffic, use the following command.
ip unknown-multicast
[port PORTS] block
Configures the switch to discard unknown multicast
traffic.
PORTS: port number
ipv6 unknown-multicast
[port PORTS] block
no ip unknown-multicast [port
PORTS] block
Configures the switch to flood unknown multicast
traffic. (default)
no ipv6 unknown-multicast [port
PORTS] block
This command should not be used for the ports to which a multicast router is attached!
9.2.1.2 Forwarding Entry Aging
To specify the aging time for forwarding entries on the McFDB, use the following
command.
ip mcfdb aging-time
<10-10000000>
Specifies the aging time for forwarding entries on the
McFDB.
10-10000000: aging time (default: 300)
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