Q: All my monitored devices are DHCP based. I poll using DNS name. I am doing a simple ping to verify if they are responding or not. Last night we had a power surge or something, and all the devices grabbed new IP addresses. The next pass through, they all showed as down. It appears that when the poll cycle goes through it is looked up by IP address, not by DNS name. Based on the description of poll using DNS, I would have expected it to lookup the ip address each time it went through a poll cycle. What’s wrong?
A: Please note that, to decrease load on DNS servers, DNS requests are often cached. In such a case, the piece of software could use cached (invalid) value of DNS response.
To prevent that reliably, please stop DNS client service at the computer running IPHost Network Monitor (and set its startup option to «Manual»), and make sure that at least primary DNS server (listed to be contacted first) always returns actual response data.
Note that disabling the mentioned DNS client service could result in much more frequent requests to DNS servers.