The DNS (domain name system) monitor checks that your name servers are responding appropriately to domain lookup requests. Most sites will have at least two name servers thereby providing some level of redundancy in the event of one DNS server failing. However since this redunancy should ensure your site continues to function, you could be blissfully unaware that a name server is offline until it is to late and another fails thereby bringing yur entire site down. Using this monitor allows you to repair or restart any failing name server sooner rather than later, helping to ensure your site (or possibly many sites) does not go offline due to multiple failed dns servers. If you run your DNS server on a non-standard port then you will need to use our DNS - Port monitor.