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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?

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How many VM's share the host network card with this particular one? – DanBig Mar 31 '10 at 15:08
The VM has a dedicated interface for Internet and LAN – stead1984 Mar 31 '10 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 '10 at 17:54

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

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I don't think it's that as we are using a DHCP server with a 2 week lease. – stead1984 Mar 31 '10 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. – psynnott Mar 31 '10 at 16:31
A good reason DHCP servers should ping-test before handing out IPs. – Chris S Jun 26 '10 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 '10 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.

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up vote 0 down vote accepted

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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