Client cannot resolve our domain names

But can connect via IP address - why?

[groovyhippo]

I have a dedicated server which is running around 90 sites off 1 IP address.

One of my clients cannot browse to ANY of my sites - she gets a "server cannot be found" error. When I ask her to put the IP address in her browser she connects fine, so it seems to be that she is not resolving the domain names correctly. But what would cause this? She can browse absolutely any other site fine, and it seems that everybody else can get to my sites. Any ideas what might be causing this?

She is using Safari on a Mac if that's relevant.

[raywood]

Could it be that the browser doesn't support host headers? I'm not familiar with Safari, but when you run more than one domain on the same ip you usually use host headers to distinguish them from each other.

[chrisnrae]

I had this happen once before. I changed hosts on one of my sites and three weeks later, everyone could see it via the domain but me. I could view via IP, but not via the name. It turned out to be my ISP. Something to do with their DNS not updating - they alternate between four and I was using one that hadn't updated. They manually had me switch it to an updated one and it worked. Don't know if she is having the same issue, but she may want to try and see if it could be the ISP.

[groovyhippo]

But a lot of these sites have been up and running on the same host/server/IP for a couple of years or more. Surely no-one's DNS could be that far out of date?

[chrisnrae]

Ahh, gotcha. Sorry. The original post didn't mention if anything had recently changed, so I just threw it out there. ;) You're right, a host is seriously unlikely to be that far out of date.

[py9jmas]

Could it be that the browser doesn't support host headers? I'm not familiar with Safari, but when you run more than one domain on the same ip you usually use host headers to distinguish them from each other.

Safari supports HTTP/1.1 (and therefore sends a Host: header).

If the client sends a HTTP/1.0 request without the Host: header, Apache replies assuming the request was for the default virtual host (the first one defined in httpd.conf). Ie, you would get something back from the remote server, even if it was the wrong page or a 404.

[raywood]

Thanks, py9jmas. Been using host headers so long I forgot how they work. Just second nature to set them up on the web server.

[bnhall]

You could also see if the client can clear their DNS cache.

[groovyhippo]

Well I'm not even sure how to do that myself, let alone my client!

Do you mean at the level of the ISP? Or on the client's network?