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SmartPLC DataLine with EtherNet/IP device interface
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8.3
Address assignment in Ethernet networks
39571
In the Ethernet network every IP address MUST be unique.
The following IP addresses are reserved for network-internal purposes and are therefore not
allowed as an address for participants: nnn.nnn.nnn.0 | nnn.nnn.nnn.255.
Only network participants whose subnet mask is identical and whose IP addresses are
identical with respect to the subnet mask can communicate with each other.
Rule:
If part of the subnet mask = 255, the corresponding IP address parts must be identical.
If part of the subnet mask = 0, the corresponding IP address parts must be different.
If the subnet mask = 255.255.255.0, 254 participants communicating with each other are
possible in the network.
If the subnet mask = 255.255.0.0, 256x254 = 65 024 participants communicating with each
other are possible in the network.
In the same physical network different subnet masks of the participants are allowed. They
form different groups of participants which cannot communicate with groups of participants
having other subnet masks.
In case of doubt or problems please contact your system administrator.
Examples:
Participant A
IP address
Participant A
Subnet mask
Participant B
IP address
Participant B
Subnet mask
Communication of
participants possible?
192.168.82.247
255.255.255.0
192.168.82.10
255.255.255.0
Yes, 254 participants possible
192.168.82.
247
255.255.255.0
192.168.82.
247
255.255.255.0
No (same IP address)
192.168.82.247
255.255.
255
.0
192.168.82.10
255.255.
0
.0
No (different subnet mask)
192.168.
82
.247
255.255.255.0
192.168.
116
.10
255.255.255.0
No (different IP address range:
82 vs. 116)
192.168.222.213
255.255.0.0
192.168.222.123
255.255.0.0
Yes, 65 024 participants
possible
192.168.111.213
255.255.0.0
192.168.222.123
255.255.0.0
Yes, 65 024 participants
possible
192.168.82.247
255.255.255.0
192.168.82.
0
255.255.255.0
No; the whole network is
disturbed because the IP
address xxx.xxx.xxx.0 is not
allowed