I have a test lab set up running a virtualized windows 2003 domain on a CentOS 5.3(xen) host and am experiencing connectivity problems with guests running on other hosts that are part of the same domain.

Here's the setup:

On Computer A I have CentOS 5.3 running as the host and have virtualized windows 2003 servers for a primary domain controller, a backup domain controller and an exchange server. The primary domain controller also acts as a WINS and dns server. The windows domain appears on a separate subnet from my company's corporate network. Connectivity to any of the virtualized guests on Computer A is fine (remote desktop, ping, what have you).

I have another host computer (Computer B) that also has a virtualized Windows 2003 server guest that is part of the same domain. However, connectivity to that guest is flaky at best. I continuously get at least 60% packet loss when I try to ping the guest, and due to that flakiness I can not access any of the services that it runs (remote desktop, web).

Now here's the interesting part. It seems to affect only machines running on a different computer than the domain controller that are in the same domain. On Computer B there is another Windows 2003 guest that is not part of the test domain and is on my corporate network. There's no connectivity issues with that guest machine.

The problem does not seem to be specific to Computer B either. I created a test VM on my local computer within the test domain and it exhibits the same behaviour as the guest in Computer B.

A couple of items to note: - Host OS on both Computer A and B are the same CentOS 5.3 64 bit - Guest OS is Windows 2003 64 bit and 32 bit (the guest on Computer B is 32 bit) - Guest OSes are all up to date (as of Monday) - Host OS on Computer A was upgraded from CentOS 5.2 to 5.3

Update: Sorry I did not follow up with the comments from below. Computer A and B have been moved to their own dedicated switch and the problem has gone away. I'm not sure what the underlying problem(s) were though