Intermittent DNS resolve problems

[marcoh]

I wonder if anyone out there has encountered similar problems to what I have been experiencing over the last few months.

On my server I have five accounts, the main account and one domain using the servers allocated ip number. The other three accounts have their own ip numbers allocated

At regular intermittent intervals, the accounts which have the seperate ip numbers just vanish from some isps, usually for periods of upto 1 hour. (tracert says unable to resolve host) During the same time, you can access the sites using the ip numbers.

The main isp where this has been noticed from is plus.net, however, there have been customers using aol who have also advised of the sites being down. So it doesn't look like a specific hosts dns at fault.

Within the same period however, there is access information in the logs for these domains, so the sites are not totally invisible to the rest of the world. Only to some isps.

This is where it becomes strange.

The main servers site and the other domain which is on the main servers IP number remain visible at all times.

It is only the three accounts with their own ip numbers allocated which appear to be effected.

The server is running its own nameservers and checks on the effected domains using dnsreport etc.. show they are setup correctly with A records etc and are pointing to the servers correct nameserver ips.

If there is anyone out there who has had similar problems and could point me in the right direction it would be appreciated.