MDI / MDI-X autocrossover
With the MPI/MDI-X autocrossover function, the send and receive contacts of an Ethernet port 
are assigned automatically. The assignment depends on the cable with which the 
communications partner is connected. This means that it does not matter whether the port is 
connected using a patch cable or crossover cable. This prevents malfunctions resulting from 
mismatching send and receive wires. This makes installation much easier for the user.
Note
Formation of loops
Please note that the direct connection of two ports on the IE switch or accidental connection 
over several IE switches causes an illegal loop. Such a loop can lead to network overload and 
network failures.
Autonegotiation
Autonegotiation means the automatic detection/negotiation of the transmission rate and the 
operating mode of ports at the opposite end. This makes it possible to configure different 
devices automatically.
Two components connected to a link segment can exchange information about the transfer and 
can adapt their settings to each other. The mode with the highest possible speed is set.
Note
● If a port is set permanently to full duplex, the connected partner port must also be set to full 
duplex.
● If a port operating in the "Auto negotiation" mode is connected to a partner port that is not 
operating in the"Auto negotiation" mode, the partner port setting must be fixed at 100 Mbps 
or 10 Mbps half duplex mode.
● If you disable the "Auto negotiation" function, the "MDI/MDI-X autocrossover" function is 
also turned off. Then use a crossover cable.
Connecting up
6.2 Industrial Ethernet
SCALANCE XB-200
36 Operating Instructions, 03/2020, C79000-G8976-C359-09