User manual

FL SWITCH LM
2-8
PHOENIX CONTACT 7278_en_01
2.2 Frame Switching
The managed switch operates in store-and-forward mode. When receiving a data packet,
the switch analyzes the source and destination addresses. The switch stores up to
1023 MAC addresses with an aging time of 48 seconds in its address table.
2.2.1 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.
2.2.2 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 1023 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.
2.2.3 Learning Addresses
The LMS independently learns the addresses for termination devices, which are connected
via a port, by evaluating the source addresses in the data telegram. When the LMS
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 LMS can learn up to 1023 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 (48 seconds, aging time).
All learned entries are deleted on a restart.