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Allow DNS lookup of the Telnet client address. Windows systems only.


[Telnet]    DNSLookup=n

n is either the string ON or OFF. The default value is ON.


DNSLookup enables or disables DNS lookup of the client address in the telnet daemon before passing the address to the InterSystems IRIS® data platform process that was created to service the connection. This determines the format of the client address returned by $IO and $ZIO in the InterSystems IRIS process.

When DNSLookup is enabled, a DNS lookup of the client address is performed, and the client name is passed to InterSystems IRIS. When DNSLookup is not enabled, no DNS lookup is performed, and the client address is provided in either dotted decimal format (if the connection was via IPV4) or in the colon separated hexadecimal format (if the connection was via IPV6). You should disable this parameter if a DNS server is not available to do the lookup, because a long delay will occur during login if the DNS server is not available.

InterSystems IRIS Telnet settings apply only to Windows configurations in which InterSystems supplies the Telnet servers. This parameter is ignored for UNIX® systems.

Changing This Parameter

On the Telnet Settings page of the Management Portal (System Administration > Configuration > Device Settings > Telnet Settings), in the DNS Lookup field, choose ON or OFF.

Instead of using the Management Portal, you can change DNSLookup in the Config.TelnetOpens in a new tab class (as described in the class reference) or by editing the CPF in a text editor (as described in Editing the Active CPF).

If you edit this setting, you must restart InterSystems IRIS to apply the change.

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