Detecting Ip Address Conflicts; Description Of Ip Address Conflicts - Hirschmann RS20 User Manual

Operation diagnosis
9.9 Detecting IP address con-
flicts

9.9.1 Description of IP address conflicts

By definition, each IP address may only be assigned once within a subnet-
work. Should two or more devices erroneously share the same IP address
within one subnetwork, this will inevitably lead to malfunctions, including
communication disruptions with devices that have this IP address.In his In-
ternet draft, Stuart Cheshire describes a mechanism that industrial Ethernet
devices can use to detect and eliminate address conflicts (Address Conflict
Detection, ACD).
Mode
enable
disable
activeDetectionOnly Enables active detection only. After connecting to a network or after an
passiveOnly
Table 17: Possible address conflict operation modes
Basic Configuration L2P
Release 4.2 07/08
Meaning
Enables active and passive detection.
Disables the function
IP address has been configured, the device immediately checks whether
its IP address already exists within the network.
If the IP address already exists, the switch will return to the previous con-
figuration, if possible, and make another attempt after 15 seconds. At any
rate, the Switch will not connect to the network with a duplicate IP ad-
dress.
Enables passive detection only. The device listens passively to the net-
work to determine whether its IP address already exists. If it detects a du-
plicate IP address, it will initially defend its address by employing the ACD
mechanism and sending out gratuitous ARPs. If the remote connection
does not disconnect from the network, the management interface of the
local device will then disconnect from the network. Every 15 seconds, it
will poll the network to determine if there is still an address conflict. If there
isn't, it will connect back to the network.

9.9 Detecting IP address conflicts

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