if you mean for udp or tcp inputs, check the specifications
http://docs.splunk.com/Documentation/Splunk/6.0/admin/Inputsconf
connection_host = [ip|dns|none]
* "ip" sets the host to the IP address of the system sending the data.
* "dns" sets the host to the reverse DNS entry for IP address of the system sending the data.
* "none" leaves the host as specified in inputs.conf, typically the splunk system hostname.
* Defaults to "dns".
if you mean for udp or tcp inputs, check the specifications
http://docs.splunk.com/Documentation/Splunk/6.0/admin/Inputsconf
connection_host = [ip|dns|none]
* "ip" sets the host to the IP address of the system sending the data.
* "dns" sets the host to the reverse DNS entry for IP address of the system sending the data.
* "none" leaves the host as specified in inputs.conf, typically the splunk system hostname.
* Defaults to "dns".