Mitsubishi Electric MELSEC-L Series - IP Address in Use Detection Function

192
14.6 IP Address in Use Detection Function
If different stations in the same network use the same IP address, the address in use can be detected. This prevents a
network from stopping due to incorrect IP address.
When the connected device with the same IP address does not support the IP address in use detection function, the
error is not detected.
(1) Checking the IP address already in use
The following two methods are available:
• Checking buffer memory areas
• Checking using the Ethernet diagnostics
(a) Checking buffer memory areas
Both the station already connected to the network and the station with the same IP address (station connected
to the network later), and the MAC addresses of the stations with the same IP address can be checked. The
destination IP address can be checked only in the station with the same IP address (station connected to the
network later).
Buffer memory area
Buffer memory
address
Description
Destination IP address (stored in the station with the same IP address
connected to the network later.)
234 (EA
H
)
The third and fourth octets of the IP
address
235 (EB
H
)
The first and second octets of the IP
address
IP address status
storage area
The MAC address of the station that has been
already connected to the network (stored in the
station with the same IP address connected to
the network later).
21121 (5281
H
)
The fifth and sixth octets of the MAC
address
21122 (5282
H
)
The third and fourth octets of the MAC
address
21123 (5283
H
)
The first and second octets of the MAC
address
The MAC address of the station with the same IP
address connected to the network later (stored in
the station that has been already connected to
the network).
21124 (5284
H
)
The fifth and sixth octets of the MAC
address
21125 (5285
H
)
The third and fourth octets of the MAC
address
21126 (5286
H
)
The first and second octets of the MAC
address
IP address:
MAC address:
00 26 92 89 2E 89
IP address:
10.97.24.3
MAC address:
00 1A 4D 5D 5D D8
IP address:
10.97.24.2
MAC address:
00 26 92 45 16 CC
IP address:
MAC address:
00 26 92 DE 26 90
This station
cannot be
connected to
the network,
resulting in
an error.
The module
connected later
The station that has been already
connected to the network continues
communications even if the station
with the same IP address is connected.
If a station and another station with the same
IP address exist on the same network, another
station cannot be connected to the network.
(The COM.ERR.LED turns on and COM.ERR.LED
turning on check (X1C) turns on.)
10.97.24.1 (overlapped) 10.97.24.1 (overlapped)