What is this?

This knowledgebase contains questions and answers about PRTG Network Monitor and network monitoring in general.

Learn more

PRTG Network Monitor

Intuitive to Use. Easy to manage.
More than 500,000 users rely on Paessler PRTG every day. Find out how you can reduce cost, increase QoS and ease planning, as well.

Free Download

Top Tags

View all Tags

DHCP Renew Fails on Win 2008 R2 SP1 Hyper-V when PRTG probe running



This problem is a little convoluted, and I'm not quite sure where the root of the problem lies.

I have PRTG running on a Hyper-V VM running Win 2008 R2. This sits on a Hyper-V cluster. It has been running fine for several months. A couple of weeks ago I installed Windows SP1 on both the client and Hyper-V host machines. Since then, the client machine has fallen off the network every 4 days. It loses it's DHCP assigned IP address replacing it with a 169 autoconfiguration IP. The only way I have found to get it's IP address back is a reboot of the VM.

If I try to do a manual DHCP renew with ipconfig /renew it generates an error "An error occurred while renewing interface...An attempt was made to access a socket in a way forbidden by its access permissions" and reverts to a 169 IP. My DHCP lease is set to 8 days, so I'm fairly sure that it's dropping connection after 4 days as this is 50% of the DHCP lease at which point it contacts the server to renew the lease.

I came accross http://support.microsoft.com/default.aspx?scid=kb;EN-US;974909 which provides a hotfix for pre SP1 Hyper-V machines which lose network connectivity when under high network load, so I suspect this may be a related problem. But since the files in the hotfix are considerably older than those in SP1, I'm reluctant to apply the hotfix.

If I disable the PRTG probe service, the problem seems to go away, so I suspect it's the large number of connections PRTG makes (I have a couple of hundred sensors) that's causing the problem.

Has anyone come accross this issue or have a fix?



169 dhcp prtg windows-2008-r2-sp1

Created on Mar 1, 2011 2:13:28 PM

1 Reply



I've done a little more troubleshooting here. By reducing my DHCP least time I've confirmed that the server only loses its IP when PRTG probe is running.

The hotfix I mentioned above is included in SP1, so that's no help. Thinking that the problem might be related to SP1, I uninstalled this from both the guest VM and the Hyper-V host server, but the problem remains.

Created on Mar 2, 2011 1:28:10 PM

Disclaimer: The information in the Paessler Knowledge Base comes without warranty of any kind. Use at your own risk. Before applying any instructions please exercise proper system administrator housekeeping. You must make sure that a proper backup of all your data is available.