GFK-2571A
Chapter 4 System Operation
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4
Duplicate PROFINET Controller IP Address
The PNC detects that a network device has the same IP address as its own during powerup, when a
new hardware configuration is downloaded from the programmer, and during operation when a
device with a conflicting IP address announces its presence
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on the network.
When a duplicate is detected during powerup, PNC reset, or new hardware configuration store, the
PNC:
logs a Duplicate IP Address Detected fault for itself,
does not connect to any configured PROFINET IO Devices,
periodically queries the network for resolution of the IP address conflict.
When a duplicate IP address is detected after the PNC has established connection to configured IO
Devices, the PNC:
logs a Duplicate IP Address Detected fault for itself,
disconnects from all currently-connected PROFINET IO Devices,
logs a Loss of Device fault for each PROFINET IO Device that was disconnected,
logs an Addition of Device fault for each connected PROFINET IO Device that was
previously lost to indicate that device is back online.
When the IP conflict is resolved, the PROFINET Controller:
logs a Duplicate IP Address Resolved fault for itself,
attempts to re-connect all configured PROFINET IO Devices,
logs an Addition of Device fault for each connected PROFINET IO Device to indicate that
device is back online.
Note:
Power cycling a rack that has a PNC with the same IP address as another node on the
network will result in two Duplicate IP Address Detected faults in the I/O Fault table. This is normal
behavior that occurs because the PNC retains IP parameters through a power cycle and attempts to
exist on the network before receiving a new configuration from the CPU. The first fault occurs before
the PNC receives the new configuration and the second fault occurs after the PNC receives its new
configuration. Both faults result in the PNC not attempting to connect to the network.
Resolving Duplicate IP Addresses
When an IP address conflict exists, IP-based network communication with the device(s) may be
disrupted. The IP address conflict should be resolved by disconnecting one of the offending devices
from the network or assigning each a unique address. The Duplicate IP Address Detected fault lists
the MAC address of the offending devices in bytes 8
– 13 and 14 – 19 of the Fault Extra Data. The
Discovery and Configuration Protocol (DCP) tool in Proficy Machine Edition may be useful to identify
PROFINET devices on the network with conflicting IP addresses.
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The PROFINET Controller uses the ARP protocol to detect duplicate IP addresses. Devices that issue a gratuitous
ARP to announce their presence on the network are detected.
