Enhanced Host Name Resolution

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In some scenarios, the host names listed in the tables below are recognized in addition to normal (system) host resolution process. For performance reasons (because the normal host resolution can take considerable time), the enhanced host name resolution takes place first; that is, if the host name is one of those listed in the corresponding table, it is resolved using the enhanced host name resolution table, and the normal host name resolution will not take place.

Depending on the context, the program might be resolving the host name either to IP address or to the MAC (physical) address. A different set of host names is recognized in each case.

Resolution To IP Address

In this case, the outcome of the enhanced host name resolution may be either an IPv4 address, or an IPv6 address. If the host name has entry only under one of the IPv4 or IPv6 columns, this entry is used. If it has entries under both columns, a "preferred" entry will be used. Which one it is depends on the context.

Host Name IPv4 Address IPv6 Address
ip6-allhosts ff02::3
ip6-allnodes ff02::1
ip6-allrouters ff02::2
ip6-localhost ::1
ip6-localnet fe00::0
localhost ::1
localhost.localdomain ::1
localhost6 ::1
localhost6.localdomain6 ::1

When used:

  • OPC UA PubSub connection resource URIs with scheme "opc.udp". IPv4 address is preferred, unless a (boolean) PubSub connection property UdpPreferIpv6 is set to 'true'.

Resolution To MAC Address

Host Name MAC Address
eth-broadcast FF-FF-FF-FF-FF-FF

When used:

  • OPC UA PubSub connection resource URIs with scheme "opc.eth".