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Can't resolve new company subdomain

For some reason, we can't access our new subdomain internally, but external PC's can access it fine.  Here's some info to help:

Our website is hosted by our ISP
Our website is www.company-solutions.com (changed)
Subdomain is www.subdomain.company-solutions.com
Our Internal Domain is called company-solutions.com
Our Domain Controller also hosts DNS and is a Windows 2003 SBS
Our company website can be accessed internally, but as soon as we add the subdomain, we get:

Internet Explorer cannot display the web page

Any ideas how to fix this?
1 Solution
Your internal domain shouldn't be the same as your external domain.  When it is problems like this arise ;)

You need to setup the subdomain on your Domain Controller that is hosting DNS.

Your local DNS server will not forward requests for it's own domain or sub-domains, it thinks it should be authoritative, and it's right.
You will have to add the entry to your internal DNS server.  If you look at your DNS server settings you will probably find that your DNS server has an entry for www which will point to the IP address of your company website.

Because your internal domain is authorative for company-solutions.com the same as your internet presence, the IP address will not be automatically entered into your DNS table when a change is made externally.
Open DNS management (dnsmgmt.msc) and make sure you have forward lookup zones created for the following, with the default a record your ISP's web hosted IP address:


You can create A records for the following (with the same IP address) under that forward lookup zone:


All of those should point to your ISP's IP address.  To make sure of what it is, ping it from an external computer.
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-Juddy-Author Commented:
I do have a www as you say which points to the IP address of our (hosted) website.  When I try to add a new Host (A) record like the other one the following happens:

It doesn't create a similar 'textpad' type icon, but a yellow folder called the subdomain.  If I don't use the PTR record tick box this yellow folder is created, but  If I tick PTR it says it cannot create the PTR record, because the referenced reverse lookup zone cannot be found.
-Juddy-Author Commented:
In DNS we have the following folder structure:

Forward Lookup Zones
          (WWW record is within here, Host (A))

dont worry about the PTR record.

Once you have added the subdomain - which will be another folder, you will need to go into that folder and add the Ip address(A Record) for the server on that subdomain.  e.g.  www.subdomain.company-solutions.com

-Juddy-Author Commented:
Perfect answer, thanks for your help.

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