Publication 1785-UM012D-EN-P - July 2005
Communicating with Devices on an Ethernet Network 11-15
Using Domain Name
Service
DNS allows an Internet Protocol (IP) address in symbolic form to be
converted into the equivalent numeric IP address. For the PLC-5 controller,
this conversion is a service provided by a remote host on the network.
With this release of Ethernet PLC-5 controllers and release 5.20 or greater of
RSLogix programming software, you may enter the symbolic form of the IP
address as the IP address in the Message Block.
The Channel Configuration feature in RSLogix5 programming software allows
you to configure a primary and secondary DNS server, as well as a Default
Domain Name (for example, cle.ab.com).
DNS names consist of a label name and a domain name. When programming
the message instruction, you can enter the full label and domain name (for
example, Motor1.cle.ab.com) or just the label name (Motor1). The default
domain name (cle.ab.com) is appended to the label name.
Label names must start with a letter and can only consist of letters, digits and
hyphens.
When a message instruction with a label name is first used, the PLC-5
controller verifies that label name with the name servers. When the IP address
is returned, the connection is made. After the connection is made, subsequent
message instruction will not require label name verification.
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