I just started working for a customer who had a previous IT company setup their domain. They have about 30 computers in their domain and are running Server 2008 with Microsoft Exchange 2007.
Their previous IT guy named their domain with a .com instead of a .local, despite the fact that they DO NOT OWN the actual .com address. For sake of argument, we will call their domain: contoso.com. All networks I do work on end in .local.
This causes problems because all computers in a domain are technically subdomains. So if your domain is contoso.local and your computer name is computer1, the FQDN of your local computer is computer1.contoso.local. When you try and access a network share on computer2 or ping computer2, it looks up the FQDN in DNS to resolve the IP address. Because they are using contoso.com, it attempts to lookup computer2.contoso.com. As long as the computer has registered with DNS and it does exist, it will be found.
When I ping somethingthatdoesntexist.contoso.com, instead of failing to ping, I literally start getting ping responses back from a public IP address. The only DNS settings on all of the computers in the network point to our domain controllers. Both domain controllers only point to themselves. There IS a fowarder in the DNS Server in the primary domain controller to our ISP's DNS servers in addition to both opendns servers as backups. If I did not have any forwarding, nothing on the network would be able to resolve internet IP addresses.
However, programs like Outlook 2007 which automatically try and configure based on guessing subdomains are in for a rude awakening. When an address does not exist in the local DNS server for say, mail.contoso.com, it forwards out to our ISP's DNS servers which report back a public IP address (not owned by my customer). This is causing lots of little headaches and annoyances, besides the fact that Outlook 2007 will not autoconfigure.
I have resigned myself to the fact that changing from .com to .local would be too much work, especially since Exchange is involved. So my question is, how do I disable DNS from forwarding requests ending in contoso.com? This would be a quick fix.
Also, I would be open to any suggestions on switching from .com to .local if it doesn't involve scratching the current domain and recreating everything.
(In response to Joseph Kern...)
Have explained the situation to the customer. This is one of a bunch of major problems that we are dealing with. This is why the last guy was fired. Unlike the other problems, I have no idea where to start with this one.