Ip Configuration And Dhcp; S7 Connections And Dhcp; Address Assignment Via Dhcp- Gigabit Interface; Restart After Detection Of A Duplicate Ip Address In The Network - Siemens S7-400 Equipment Manual

Configuration and operation
6.5 Interface configuration
6.5.2

IP configuration and DHCP

6.5.2.1

S7 connections and DHCP

Configured S7 connections cannot be operated if the IP address is assigned over DHCP
Note
If you obtain the IP address using DHCP, any S7 connections you may have configured will
not work. Reason: The configured IP address is replaced by the address obtained via DHCP
during operation.
6.5.2.2

Address assignment via DHCP- gigabit interface

Static DHCP
When assigning addresses using DHCP on the gigabit interface, the module should be
assigned a fixed IP address in the DHCP server (static DHCP). This also applies to the default
router.
A modified IP address is adopted only following a STOP → START change.
Note the restrictions when a protection level is configured for the CPU. See section Effects of
protection levels (Page 57) for information on this.
6.5.2.3

Restart after detection of a duplicate IP address in the network

To save you timeconsuming troubleshooting in the network, the CP detects double
addressing in the network.
Behavior during operation (CP in RUN)
If the CP detects double addressing on the network (new node with an IP address that has
already been assigned), a message is generated in the diagnostics buffer and the bus fault
LED lights up.
To acknowledge the bus fault LED in RUN mode, set the CP to STOP and then restart it.
After the device with the duplicate IP address has been removed from the network, the bus
fault LED goes off automatically.
Behavior when the CP starts up
If duplicate addressing is detected when the CP starts up, the CP remains in STOP. The bus
fault LED is lit and a diagnostics buffer entry is generated. The CP only starts up after the
duplicate addressing problem has been eliminated.
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Equipment Manual, 03/2023, C79000-G8976-C256-07
CP 443-1 Advanced