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Multicast filtering
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7 Multicast filtering
7.1 Basics
Multicast Multicast applications, unlike unicast applications with point-to-point communication, do not
transmit their data with the MAC address of the destination, but with an independent multi-
cast group address. Always using wireless communication, a station transmits one data
packet that is received by one or more receiving stations.
Advantages:
1
If, for example, a data packet of a transmitter is to be transmitted to eight receivers, the
same packet does not have to be sent eight times to the addresses of all eight devices.
Instead it only needs to be sent once to the address of the multicast group that includes
the eight devices.
2 When using multicast communication and filtering, the bandwidth requirement for data
transmission is reduced because each packet is only transmitted once.
7.2 Enabling the web pages for multicast filtering in
WBM
Activate WBM for the switches, e.g., using Factory Manager. Switch to the “General Con-
figuration” menu, then select the “User Interfaces” page. Activate “Multicast Filtering” and
confirm by entering your password.
7.3 Static multicast groups
Static multicast groups must be created manually on every switch, and all ports that are
used to contact group members need to be added. The advantages of static groups are:
1
Easy specification of network paths on which the multicast data traffic of known groups
is limited.
2 No querier required (see “Query” on page 145).
The following marginal conditions must be observed:
–
Precise network documentation for path specification is required.
– Possible redundant paths due to Spanning Tree must be taken into account during port
assignment.
– For network modifications and, during servicing or expansion, the multicast data paths
must be restored.
A maximum of 128 multicast groups can be created automatically for IGMP snooping. In
addition, a maximum of 20 static groups can be created.
When activating “Multicast Filtering” under “General Configuration, User Interfaces”, the
multicast mechanism is not activated. In the WBM menu, the “Multicast” page - under
which the function can be configured and activated - is enabled.