DNS Requests
To qualify the address of a module, use DNS addressing to specify a host name for a module, which also includes specifying a domain name and DNS servers. DNS addressing makes it possible to configure similar network structures and IP address sequences under different domains.
DNS addressing is necessary only if you refer to the module by host name, such as in path descriptions in MSG instructions.
For more information on DNS Addressing, see:
- EtherNet/IP Network Configuration User Manual, publication ENET-UM001
DNS requests can be generated from port 1 or port 2.
IMPORTANT:
With
ControlLogix®
5590 controllers, the Ethernet ports on the controller itself are labeled 1 and 2. In programming and communication software, the ports are described as A1 and A2.DNS Request Generated From Port 1
The following apply when port 1 generates the DNS request:
- If the DNS server address is in the local subnet of port 1, DNS requests leave through port 1.
- If port 2 is enabled and the DNS server address is in local subnet of port 2, DNS requests leave through port 2.
- If the DNS server address is outside of all local subnets, DNS requests leave through port 1 towards port 1 default gateway.
DNS Request Generated From Port 2
The following apply when port 2 generates the DNS request:
- If port 1 is enabled and the DNS server address is in local subnet of port 1, DNS requests leave through port 1.
- If the DNS server address is in local subnet of port 2, DNS requests leave through port 2.
- If port 1 is enabled and the DNS server address is outside of all local subnets, DNS requests leave through port 1 towards port 1 default gateway.
- If port 1 is disabled and the DNS server address is outside of all local subnets, DNS requests leave through port 2 towards port 2 default gateway.
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