Must run ipconfig /flushdns in order to access subdomains of my main domain.. Why?

I run 5 computers on a home business network and access the internet using a DSL Router all networked together. We use MS live One care for our firewall/adware/virus protection. We have a leased server on the internet with several domains (30approx) all share the same ip. One particular domain will cause the "file cannot be found" error only when we access the subdomains of the main. We must run the ipconfig /fushdns under the command prompt in order for the sites to be accessable again .. This happens several times a day, only on one domain only on the subdomains. we have 3 of our machines running Vista and 2 running XP  both OSs have the same problem. The error does not occur network wide, some can access and some cant. It doesnt seem to happen  on other the domains on our server with subdomains but it might, we dont access the other subdomains as often as we do these
Who is Participating?

[Product update] Infrastructure Analysis Tool is now available with Business Accounts.Learn More

I wear a lot of hats...

"The solutions and answers provided on Experts Exchange have been extremely helpful to me over the last few years. I wear a lot of hats - Developer, Database Administrator, Help Desk, etc., so I know a lot of things but not a lot about one thing. Experts Exchange gives me answers from people who do know a lot about one thing, in a easy to use platform." -Todd S.

So let me understand what you are saying:

You have a web server that exists somewhere on the internet. It hosts a bunch of websites. They all use the same IP with different host headers.

You have several computer at home. You are in a WORKGROUP setup at home.

One one of the domains that is hosted on the web server you have intermittant trouble accessing a subdomain. Running "ipconfig /flushdns" resolves the issue when you are unable to access it. No other domains have this issue. The issue affects all workstations.

Is that correct?

Are all your computers set to DHCP? If so, what device is serving DHCP? Also, are they pointing to the ISP's server for DNS?
That's a likely scenario - your DHCP is probably pointing your DNS to the MS gateway which is maybe doing the wrong thing like rewriting the TTL (time to live) of your DNS entry. But you probably need to do some testing.

It's also a common thing for hosting providers to have an extremely short TTL for domains. But we're assuming the IP is actually changing between DNS queries. You should compare a
'nslookup whateverdomain' when it's not working, then do the flushdns to fix it, and the again
'nslookup whateverdomain' to see if it changes.
adnetworkAuthor Commented:
My DHCP server is the Netropia 2247-02 router for the DSL ..
 I did a nslookup for the subdomain while it was working and I attached the response .
It hasnt stopped working yet today but I will post that nslookup response when it does
Our LAN address set in the router is  mask
DHCP is set at Starting IP is   -   ending IP is
Our Novell 5 Server is set to IP  mask  

I dont have any other settings configured in the Netopia router and perhaps I need to.. but I dont understand the setup well enough to know what needs to be done
Webinar: Miercom Evaluates Wi-Fi Security

It's not just about Wi-Fi connectivity anymore. A wireless security breach can cost your business large amounts of time, trouble, and expense. Plus, hear first-hand from Miercom how WatchGuard's Wi-Fi security stacks up against the competition in our upcoming webinar!

Can you show us your DHCP Server options page in your Netopia device?
adnetworkAuthor Commented:
Here are the screens under the DHCP Setup
You said that your Novell server is at a .5 address, yet you also have that address included in your DHCP range. I am not sure if that is causing this particular issue, but I want you to change the scope of your DHCP server to something like: -

It seems like 25 addresses are more than enough (since you are only using 4 currently).
Also, to rule out the possiblity that it is an issue with your DNS server, you can modify the DNS settings on your Netopia device to:

These are free DNS server ran by "Open DNS"

Once you make these change then run an "ipconfig /release && ipconfig /renew" from the command prompt of each machine.
Obviously make a note of any settings you change so you can revert back if there are any issues.
adnetworkAuthor Commented:
I have set the ip scope to the 25 ips and am hesitant about the dns settings.. they have a notation with in the configuration screen not to change the dns if your internet provider dynamically serves your dns to the router.. how would I test for this ?

I have not had an incident where the sub domain has been inaccessible yet today good sign..
It is just their way of saying "If you don't know what this is, then don't touch it.".

It will be fine, just record the numbers and what they are before you change them so you can revert back if need be.

Experts Exchange Solution brought to you by

Your issues matter to us.

Facing a tech roadblock? Get the help and guidance you need from experienced professionals who care. Ask your question anytime, anywhere, with no hassle.

Start your 7-day free trial
adnetworkAuthor Commented:
Thanks for walking me thru the solution .. quickly and easily.. I appreciate the help.. I have switched everything and it has been working without incident for a few days now.. If I have any other problems I will re-post..

thanks, again
It's more than this solution.Get answers and train to solve all your tech problems - anytime, anywhere.Try it for free Edge Out The Competitionfor your dream job with proven skills and certifications.Get started today Stand Outas the employee with proven skills.Start learning today for free Move Your Career Forwardwith certification training in the latest technologies.Start your trial today

From novice to tech pro — start learning today.