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

Operation Diagnosis
9.9 Detecting IP Address
Conflicts
9.9.1

Description of IP Address Conflicts

By definition, each IP address may only be assigned once within a
subnetwork. Should two or more devices erroneously share the same IP
address within one subnetwork, this will inevitably lead to communication
disruptions with devices that have this IP address. In his Internet 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 27: Possible address conflict operation modes
Basic Configuration
Release 6.0 07/2010
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 device will return to the previous
configuration, if possible, and make another attempt after 15 seconds.
This prevents the device from connecting to the network with a duplicate
IP address.
Enables passive detection only. The device listens passively on the
network to determine whether its IP address already exists. If it detects a
duplicate IP address, it will initially defend its address by employing the
ACD mechanism and sending out gratuitous ARPs. If the remote device
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

203