I have a virtual DC running DNS and Routing and Remote Access, that routes ALL workstations Internet traffic out to the Internet, this works fine but noticed that the Internet drops occasionally.

I've checked with our service provider (Managed Communications) and they are adamant that it's not their fault.

The Internet drops seem to affect everyone.

We also have a server configured to use the same Internet service on a different network over a site-to-site VPN connection which also suffers from packet drops.

I've spoken to Cisco and have done many tests with Cisco and they believe the problem is down to the ISP.

I'm wondering if it's a DNS issue, as the Internet service uses OpenDNS.

Any ideas?

  • How many VM's share the host network card with this particular one?
    – DanBig
    Mar 31, 2010 at 15:08
  • The VM has a dedicated interface for Internet and LAN
    – stead1984
    Mar 31, 2010 at 16:04
  • Does your site-to-site VPN actually use DNS? Probably not, and if not, you can rule out DNS right there.
    – Kyle Smith
    Jun 26, 2010 at 17:54

3 Answers 3


Check for IP address conflicts. I had exactly the same problem for hours before I figured it out.

  • I don't think it's that as we are using a DHCP server with a 2 week lease.
    – stead1984
    Mar 31, 2010 at 15:56
  • so did we, but someone in the office had a vm set up on his pc using a static ip address that nobody knew of.
    – psx
    Mar 31, 2010 at 16:31
  • A good reason DHCP servers should ping-test before handing out IPs.
    – Chris S
    Jun 26, 2010 at 17:24
  • @Chris S - I'd like to see a way for switches to report flapping ARP requests to a monitoring service too...
    – Kyle Smith
    Jun 26, 2010 at 17:55

Which NIC connects you to the internet? Make sure it's quality and try swapping it with another one. Poorly programmed drivers can cause this type of scenario.


It appears it was the ISP, managed comms after all. Turned out to be a faulty bonding device. It took 3 months to admit it was their fault.

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