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FL SWITCH IRT
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4.2 Frame switching
The FL SWITCH IRT functions according to the type of telegram and the set port configura-
tion in cut-through or store-and-forward mode. When receiving a data packet, the switch an-
alyzes the source and destination addresses. The switch stores MAC addresses in its ad-
dress table with an aging time of 40 seconds.
4.2.1 Cut-through
All multicast and unicast packets are forwarded via the cut-through method. The incoming
and outgoing ports must be set to 100 Mbps full duplex and the outgoing port must be
free/not transmitting. In the case of cut-through switching, after reading the telegram header
and detecting the target address, the data telegram is forwarded immediately to the receive
port.
4.2.2 Store and forward
If the switch receives broadcast telegrams or other port configurations are selected as 100
Mbps full duplex, the telegrams are saved and tested for validity. Invalid or faulty data pack-
ets (>1522 bytes or CRC errors) and fragments (<64 bytes) are rejected. Valid data tele-
grams are forwarded by the switch.
4.2.3 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 or
– a multicast/broadcast address
in the destination address field are forwarded via the relevant port. This is necessary if more
than one termination device is connected to one or more ports. Several independent sub-
nets can be connected to one switch.
4.2.4 Learning addresses
The FL SWITCH IRT independently learns the addresses for termination devices, which are
connected via this port, by evaluating the source addresses in the data telegrams. When the
FL SWITCH IRT 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 FL SWITCH IRT learns addresses and stores them in its table. The switch monitors the
age of the learned addresses. The switch automatically deletes address entries from its ad-
dress table that have exceeded a specific age (default: 40 seconds).
All learned address entries are deleted upon restart.