Hi i was told to mve this to the networking section please see question below Hi first of all appologies if this is not an exchange issue as it could be a hyper v issue/networking. we have a hyper v infrastructure with virtual exchange 2010 ( 1 x cas/hub 1 x mailbox) and over the past few weeks our cas server seems to stop responding to the network. you cannot ping the the server or remote on to it. the only way to get access to is via hyper v manager. when log on via hyper v manager it all seems ok. the network is there and can ping its self but it does not ping out to any other servers in the domain ( either via name or ip address). the only way i have got around this is to restart the server and it all starts working perfectly. having a look through the event viewer the only errors i see around the time it goes down are. DNS Client Even 1014 - Name resolution for the name DNS SERVER TIMED out after none of the configured DNS servers responded. i guess this is because the nothing can contact the server and the server cannot contact any other system any ideas on how to troubleshoot this. this is the only server it happens to in the whole virtual environment also as a side issue does exchange have any link to the mac address of the network card. i am concidering shutting the server down. removing all the network cards and then re appying them and setting the IP Addresses again many thanks for the help Hiten

Hi Hiten, Thanks for posting here. Are you running Hyper-V on Windows Server 2008 or 2008 R2 ? and what’s the OS running with Exchange in VM ? Have you recently modified any system setting for either Hyper-V or VM before this issue occurred ? What about the connectivity on other VMs that also hosted on this Hyper-V server with same virtual network settings? We have a update patch list in the article below which might useful for you to solve some potential virtual network issues first: Hyper-V: Update List for Windows Server 2008 R2 http://social.technet.microsoft.com/wiki/contents/articles/1349.aspx Regards, Tiger Li TechNet Subscriber Support in forum If you have any feedback on our support, please contact tnmff@microsoft.com. Please remember to click Mark as Answer on the post that helps you, and to click Unmark as Answer if a marked post does not actually answer your question. This can be beneficial to other community members reading the thread.

Hi Tiger We are running hyper v on 2008 r2 core. and the cas server on exchange 2008 r2. no changes have been made at all the only change to the whole hyper v environment that i can think of was SAN related and i had to expand one of the CSV ( Exchange was not in this CSV) other vm's on the same host as the cas server have no issue at all. we are 3 phyical host server which run about 10-12 virtual machines and it only seems to happen to the cas server. event viewser does not show anything. it only shows events as a result of network being down eg cant find dc's. cant resolve names etc. im not really sure where to start with the trouble shooting on this issue. it first occured a few months ago and put it down to a little blip and it was ok for a few months but over the last 3 weeks its been happening more and more. when you try and ping the cas server when it has this issue you dont get a normal timed out you get a destination unreachable reply. i am planning to either move the VM to another host machine or switch it off and take the network cards off it and re apply them Thanks

Hi Hiten, Thanks for update. Before we perform further operations, could you please verify the whole network settings on it when issue occurs ? cause “destination unreachable” usually indicate there might not proper route entries for source host to reach the destination address. And what kind of virtual network you set on hyper-v for this host ? is this VM host in same IP segment as other’s? or connects with other trough router ? For further troubleshooting , we may need capture and analyze traffics by network monitor: http://www.microsoft.com/download/en/details.aspx?id=4865 Regards, Tiger Li TechNet Subscriber Support in forum If you have any feedback on our support, please contact tnmff@microsoft.com. Please remember to click Mark as Answer on the post that helps you, and to click Unmark as Answer if a marked post does not actually answer your question. This can be beneficial to other community members reading the thread.

Hi Tiger the last time this happened the network seemed to be up when you were looking at the server the ip address was correctly defined and it was by the looks of it ok. but the previos times it has happened when you log on to the server and look at the network icon in the system tray you get the little circle going around and around on the network icon like it is trying to resolve the network and then when you try to get to network/connection sharing it seems to hang and freeze and the only way to resolve was a re start. the routing and everything is correctly set as its the same routing as all the other servers in the virtual environment. all the servers in the virtual environment all run on the same subnet and all have the same routes added. it just seems odd that it is only happening to this one server. so i think that might take the hyper v host out the equation? i will install and run the analyser over the wk end and see what i can find out Thanks

Tiger is this a hotfix to apply to the vitual machine in question or the host machine? Thanks

Hi Hiten, It is applied to the Windows Server 2008 R2 host with Hyper-V installed. Thanks. Tiger LiPlease remember to click Mark as Answer on the post that helps you, and to click Unmark as Answer if a marked post does not actually answer your question. This can be beneficial to other community members reading the thread.

Hi Hiten, If there is any update on this issue, please feel free to let us know. Regards, Tiger Li TechNet Subscriber Support in forum If you have any feedback on our support, please contact tnmff@microsoft.com.Please remember to click Mark as Answer on the post that helps you, and to click Unmark as Answer if a marked post does not actually answer your question. This can be beneficial to other community members reading the thread.