User manual

Startup and Functions
6874_en_09 PHOENIX CONTACT 3-31
3.3 Frame Switching
The FL SWITCH MM HS operates in store-and-forward mode. When receiving a data
packet, the switch analyzes the source and destination addresses. The switch stores up to
8000 MAC addresses with an adjustable aging time of 10 to 825 seconds in its address
table.
3.3.1 Store-and-Forward
All data telegrams that are received by the switch are saved and their validity is checked.
Invalid or faulty data packets (> 1522 bytes or CRC errors) and fragments (< 64 bytes) are
rejected. Valid data telegrams are forwarded by the switch.
3.3.2 Multi-Address Function
The switch learns all the source addresses for each port. Only packets with:
– Unknown source addresses
– A source address for this port
– A multicast/broadcast address
are forwarded to the destination address field via the relevant port. The switch can learn
up to 8000 addresses. This is important when more than one termination device is
connected to one or more ports. In this way, several independent subnetworks can be
connected to one switch.
3.3.3 Learning Addresses
The MMS independently learns the addresses for termination devices, which are
connected via a port, by evaluating the source addresses in the data telegram. When the
MMS receives a data telegram, it only forwards this data telegram to the port that connects
to the specified device (if the address could be learned beforehand).
The MMS can learn up to 8000 addresses and stores them in its table. The switch monitors
the age of the learned addresses. The switch automatically deletes address entries from
its address table that have exceeded a specific age (default: 40 seconds, adjustable from
10 to 825 seconds, aging time).
All learned entries are deleted on a restart.
A list of detected MAC addresses can be found in the MAC address table (see
"Diagnostics/MAC Address Table" Menu on page 4-39). The MAC address table can be
deleted via "Clear".