Siemens S7-300 Configuration Manual page 62

Configuring the Ethernet CP with STEP 7
3.3 Setting further CP properties
Functional description of the automatic switchover
All ports of the CP provide a 10/100 Mbps full duplex connection with autosensing and
autonegotiation of the network settings. These functions run as follows after turning on the
CP:
● The CP attempts to detect the transmission speed used by the partner.
● If detection is possible, the CP attempts to negotiate the optimum duplex mode with the
partner.
● If no negotiation is possible, the CP uses the previously detected transmission speed and
half duplex.
This takes approximately 2 seconds.
The "Automatic setting" also includes an autocrossing mechanism; this means that you can
use a crossover or straight-through cable for the connection regardless of the properties of
the partner device.
Note on the CP with a gigabit port:
The gigabit port can be set to 10 Mbps or 100 Mbps. With an automatic switchover, the CP
can achieve a setting of 1000 Mbps full duplex.
Changing to individual network settings
If you create any configuration manually, automatic switchover is no longer effective. This
also applies to the autocrossing mechanism integrated in the CP. If the connected partner
device does not support the autocrossing mechanism, you will need to use a crossover cable
(for a switch) or a straight-through cable (for an end device).
Note on the CP with a gigabit port:
The gigabit port can be set to 10 Mbps or 100 Mbps. Note the following behavior:
● "Disable autonegotiation" option is not selected
Despite individual network settings, there may be negotiation with the communications
partner resulting in a transmission speed different from the one selected.
● "Disable autonegotiation" option is selected
The set type of transmission is used.
"Disable" port option:
Depending on the module type, the drop-down list includes the "- Disable -" option. This
option, for example, allows you to prevent access to an unused port for security reasons.
Further information
Read the manual of the relevant CP for further information; see /1/ (Page 227)
62
Configuring and commissioning S7 CPs for Industrial Ethernet
Configuration Manual, 09/2013, C79000-G8976-C182-13