The Net::SNMP module calls the inet_aton() from the IO::Socket module. The actual implementation would depend on your OS. In all of the implementations that I have encountered, a dotted decimal IP address passed to the inet_aton() function does not result in a DNS look up. In your code, could you actually try passing the IP address directly as a string to the session constructor (i.e. -hostname => '10.1.10.162')? I am not sure how your "constants" are formed, but this would eliminate on possible problem area.