Siemens SINUMERIK 840DE sl Commissioning Manual page 402

Configuring the network
17.6 Station-related network diagnostics
Error
HMI displays alarm 120202 "Wait for connection to NC/PLC" and/or no values (only '#').
388
Possible error causes and remedies
Connect the service PG to the NCU via X127. Log into Linux via WinSCP or Putty.
If the set NCU mode (no DHCP) is to be kept, the fixed IP address of the NCU must be
changed.
Correctly enter the following entries into the file /user/system/etc/basesys.ini
[InternalInterface]
; With InternalIP and InternalNetMask (both must be set together),
; you can change the address on the internal/TCU/automation/system net.
InternalIP=192.168.214.1
InternalNetMask=255.255.255.0
Then restart the NCU.
Error cause 4.2
The NCU has a valid IP address in the system network, however, not the required IP address.
The NCU does not participate in DHCP operation and operates with a permanently set target
address that is different from that saved in MMC.INI in the system network - however, this is
a valid address. This is a configuration error.
Remedy 4.2
The same as for remedy 4.1
Error cause 4.3
The NCU has a valid IP address in the system network, however, not the required IP address.
The NCU participates in DHCP operation and was not able to obtain the corresponding re‐
quired IP with the target address saved in the MMC.INI; this is the reason that it was dynam‐
ically allocated an address. A reason for this could be that the required IP was configured
twice in the system network, or the required IP is not in the reserved range, but is located in
the dynamic address range. This is a configuration error.
Remedy 4.3
The same as for remedy 4.1
Error cause 4.4
The NCU has a valid IP address in the system network, however, not the required IP address.
The NCU participates in DHCP operation as DHCP client and has a required IP that has been
set but which does not match the system network. For instance, this situation occurs if a
network address was used in the system network other than the default network address, but
it was forgotten to change over the required IP of the NCU to this address range. The NCU
is allocated an IP address that matches the system network from the dynamically allocated
range, but which is different from its 'old' required IP that was not changed over. Up to and
including SW 2.4.1, in this situation, the NCU cannot be addressed in the system network.
The reason for this is that it has internally established its firewall regarding the required IP
that was entered for it, which does not match the system network - which is why it does not
respond at X120.
Remedy 4.4
The same as for remedy 4.1
Error cause 5.1
Commissioning Manual, 12/2017, 6FC5397-1DP40-6BA1
SINUMERIK Operate (IM9)