I seem to randomly receive "page cannot load, cannot connect to server" errors for sites on one of my servers. when this happens, it seems to only happen on certain IPs or IP ranges at a time. I say this because while I'll get the error from my home laptop I'll be able to access the site fine from my work computer or from an offsite VPS.
DNS records should already be fully propagated as these records were updated months ago.
I have no idea how to diagnose what's going on. Is there a tool in cpanel or outside on the web that can help me figure out what's going on?