DNS Issues with Server 2008 R2

RFC 2671.  This shouldn’t mean much of anything to most of us. This RFC Code, however, can literally mean hours and hours of frustration and troubleshooting if you have created a Server 2008 R2 domain.

Developed in 1999, Extension mechanisms for DNS aka eDNS, were designed to allow for increased functionality of the DNS protocol. They were also critical to the implementation of DNS Security Extensions (DNSSEC). Nevertheless, the protocol hasn’t really caught on and there are still thousands of devices – even ones produced today – that are not really fully compliant with the standards laid out in RFC 2671.

Naturally, the Internet itself is a inter-connected network that is literally running on loads of old and obsolete equipment.  So, it comes as no surprise that there are going to be a few problems arising from the fact that Windows Server 2008 R2, when set up as a DC with the DNS role installed and set to perform recursive lookups, has this extension to DNS enabled by default.

Not everyone, fortunately, will have issues with this as there are of course DNS servers out there that will respond properly to this type of query and respond with the IP address requested. However, if you happen to be running DNS queries against one that is non-compliant, you will end up with extremely patchy Internet service for your whole domain.

To check if this is an issue for your domain, you are going to have to run a few tests.

Open network monitor, and look at the DNS queries that you are getting. If they look like the picture below, you are probably encountering this issue.


The fix, luckily, is very simple.  Simply disable eDNS and re-enable it at some point in the future when acceptance of this protocol is a little higher.

Open up a cmd prompt and elevate it (right click on it and run it as an administrator). Then run the following command.

dnscmd /config /EnableEDNSProbes 0

This should take effect immediately.

I sincerely hope that this helps a few of you out there that are just starting to deploy Server 2008 R2 now that SP1 is out.



Outlook 2010 Auto Complete Cache Corruption

A while back, I had written a fairly complete article on restoring the Outlook auto complete cache and working with .NK2 files.  Well, just when we thought that we could all return home in a victorious Napoleonic march, our enemy defeated, our pals down in Redmond reminded us all of Waterloo.

Outlook 2010, has completely done away with .NK2 files and has unfortunately replaced it with a system that seems far from bulletproof. My recent experiences, along with thousands of others on the net, suggests that the new system is rather prone to corruption and cannot be easily fixed.

But first, in a bid to dispel some of the misinformation out there, let me briefly go over how the new system works.

Users first using Outlook 2010, or syncing it to an active sync device are immediately going to notice a new set of contacts called suggested contacts that has been auto created upon opening a new mail account.  Inside, they will quickly notice that it is populated with email addresses of people whom they may not even remember having contact with. One soon realizes that this is a contact list that is being generated based on emails that have been sent out and incoming emails that do not have a proper contact in Outlook.  This idea, actually, seems to make a lot of sense as it is an easily backed up way of managing all of those contacts that were previously stored in the Auto complete cache’s .NK2 file.  It would be easy to come to the conclusion that this is the same thing as the .nk2 cache and this is what populates it. This, however, is wrong.  While it does store similar information, there is in fact a new .dat file that has taken the place of the venerable .NK2 file, but now has a GUID attached to it that is,ostensibly,l generated based on characteristics of the profile.  Apparently, this file can be transferred around just as was done with .NK2 files, but you would have to rename it with the exact same corresponding GUID for it to work. Definitely, not as slick as the simple renaming it to the name of the profile as in previous versions of Outlook. This won’t, however, be an issue if you have transitioned to Exchange 2010 as the file is actually stored on the Exchange server and synced back down to the client allowing for your auto complete cache to follow you as part of a new profile on a second computer.  Again, this is a great idea if it weren’t for the apparent instability of the file itself.

I have been able to find very little information on the causes of the issue, and nothing at all from Microsoft, but it appears that this file syncs itself back to the Exchange server upon closing Outlook. However, if for some reason, Outlook does not close cleanly, it appears to cut short the write of this data which subsequently corrupts the file. It is at this point extremely difficult to correct the situation. 

The file is located at %appdata%\Local\Microsoft\Outlook\RoamCache  and will be the file labeled Stream_Autocomplete_<GUID>.dat. As I stated, I have yet to come across anything that immediately fixes the issue in all cases, but here are a few things to try.

First, to verify that you are having the issue in question, you will a.) have an auto-complete cache that isn’t working and b.) a Stream_Autocomplete file that is 0 bytes in size and stays that way despite adding data to the autocomplete cache during a session. With this issue, your cache will work during the duration of Outlook being opened, but then when you close outlook and reopen it, all of the data is lost. 

Anyway, here are some methods that are known to work.

1. Delete the auto-cache data through the provided menu interface provided in Outlook.  To do this,

1. In Outlook 2010, Click the File menu and Select Options.


2. In the Outlook Options window Click the Mail tab.


3. Scroll down roughly halfway until you see Send messages. Uncheck the Use Auto-Complete List to suggest names when typing in the To, Cc, and Bcc lines box.


2. The second method is to manually delete the file mentioned above. Make sure and close outlook before you do this, as it will have a lock on the file and prevent you from doing so otherwise.  This method is really the same as what happens above, but some people have actually reported that the file did not delete as it was supposed to from the GUI.

3. Rename then whole Roam Cache folder and reopen outlook.

4. Disable cached exchange mode and try methods 1,2, or 3 above and repeat until the file starts to grow in size.

And please, if anyone else has any more information on the actual root cause of this, please comment below so we can all get through this.  There are many possible culprits, but I suspect that over time we will find that it is one particular add-on or program that is causing the vast majority of cases.


Copyright © 2010 Paul Guenette and Matthew Sleno.