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We deploy virtual machines using Citrix XenServer 6.0 for our clients.

Two seperate clients experience the same issue: when a Server 2008 virtual machine is restarted, the static IP addresses (network address, subnet, gateway, primary DNS) don't appear to apply correctly as the IP's cannot be pinged, network services cannot be accessed etc.

The issue is resolved by manually switching the network adapters to DHCP, then re-setting them to the original static IP's.

While not a major issue, it's a pain when restarting servers due to Windows Updates, plus iSCSI drives need to be manually connected to Windows again via iSCSI Initiator.

We have tried removed the network adapters from the virtual machine under XenCentre but without luck.

Anyone experienced similar issues?

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Are these clients on a bridged network? How long does the arp-cache on these networks last? – Nils Aug 4 '12 at 21:29
Yes, I have had similar issues on Linux guests. The problem may have been related to a Linux kernel update. Unfortunately, I do not know the cause. – jeffatrackaid Nov 20 '12 at 15:32

I've seen similar oddities with vNICs that don't keep their MAC addresses between reboots. Take a close look at all of the details of the virtual NICs between reboots, and if they change, work out what's required to beat Xen into submission so they don't any more.

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Thanks for the feedback. I'll do a test and monitor the MAC addresses within XenCentre during reboots. – Ash Jul 11 '12 at 4:39
Don't do it in the XenCentre, look at it from the point of view of the guest. It's possible it isn't the MAC, it could be something else like a faked serial number or something. – womble Jul 11 '12 at 4:41
I got a chance last night to test this theory. ipconfig /all pre- and post-reboot showed that the MAC addresses remained the same on the network adapters. The network adapter used to connect with the iSCSI drive again had to be set to DHCP, then set back to its static IP before being able to connect the iSCSI initiator. – Ash Jul 25 '12 at 1:09

We had similar issues and an update to the network drivers on each xen host did the trick. We were using XenServer 6.0, I don't recall the exact link to the hotfix but here is a link to one for those using XenServer 6.0.2. You may also need to uninstall and reinstall XenServer tools.

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