AN-X4-AB-DHRIO (DH+) Page 27
Using DHP-HMI IP Aliasing
Overview
AN-X4-DHP supports IP aliasing, which makes it possible for Ethernet PanelViews or other
clients that don’t support CIP routing to access PLC-5s or SLCs on Data Highway Plus.
The AN-X can be configured to respond as more than one IP address, each of which is mapped to
a different Data Highway Plus station address.
IMPORTANT!
Use IP Aliasing only if the AN-X is using a static IP address.
Client applications can access Data Highway Plus stations by sending messages to these aliased
IP addresses. AN-X then sends the messages to the DHP station associated with the aliased IP
address and returns the replies to the appropriate Ethernet sender.
If multiple computers talk through an AN-X to the same PLC, the AN-X keeps track of who sent
the message and sends the reply to the appropriate Ethernet IP address.
Aliased IP addresses are configured in a simple text file, which is sent to the AN-X using the web
interface.
Aliased IP addresses must be on the same subnet as the AN-X base IP address configured on the
Configuration/AN-X Configuration page of the web interface. The upper three bytes of the alias
IP address must be the same as the corresponding three bytes of the AN-X base IP address.
Aliased AN-X IP addresses must not conflict with other devices on the Ethernet network.
The AN-X Data Highway Plus diagnostic counters increment for all messages through the AN-X.
If the destination Data Highway Plus station is offline, AN-X returns STS error 02, destination
did not acknowledge.
Ethernet/IP on Aliased Addresses
The AN-X-DHP firmware supports two Ethernet protocols that allow access to Data Highway
Plus, an older Allen-Bradley protocol called Client Server Protocol (CSP) and Ethernet/IP.
Some devices (HMIs etc.) don't support CSP, they support only Ethernet/IP.
If the device supports Ethernet/IP with CIP routing, it will work using the AN-X base address and
no aliasing is needed.
If the device supports Ethernet/IP but does not support CIP routing, we need both Ethernet/IP and
IP alias to DHP mapping for the AN-X to respond to Ethernet/IP requests on aliased IP addresses.
To enable this, add the keyword "AliasEnetIP" to the alias configuration file, configure
appropriate IP aliases and transfer the modified configuration file to the AN-X.
This is a global setting and affects all aliased addresses. The only reason not to enable it all the
time is that some devices may get confused since the AN-X reports back as an ENET module.
You can connect to a device at an aliased address using Ethernet/IP and CSP at the same time if
the HMI client supports both protocols.
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