Christos Polydorou

On my lab environment, I've configured two Active Directory sites since most enterprises have offices in more that one places. My lab however is not running 24/7 and the domain controllers in the second site are rarely turned on in order to save resources. This leads to issues with the Active Directory replication such as the "The target principal name is incorrect" error when I execute:  repadmin /syncall /AdeP. To remedy the issue, we have to reset the machine password of the domain controller that has been offline. First off, we are going to stop and disable the Kerberos Key Distribution Center (kdc) service on the problematic domain controller, in our case DC4. There may be some tickets in the cache so we should also clear them using klist purge Now it's time to change the machine password of the domain controller using the command netdom resetpwd /s:dc3 /ud:lab\administrator /pd:* Replace the "lab\administrator" with an account on your

I came across a very strange Exchange behavior the other day while troubleshooting a full access permission that was not working as expected. Although a user had been granted the full mailbox permission on a shared mailbox, when he tried to open it using OWA, he got an HTTP Error 500 message and the request failed. We'll start troubleshooting with investigating the front end IIS log files. After all, that is the first step of the request processing. Using the user's UserPrincipalName, I've managed to find the error in the log: As you can see, the HTML error code is "500" that indicates an internal server error similar to the one that the user encountered. This file however does not provide much information about the cause of the error so we'll take a look on the backend as well. After each request reaches the front end Exchange layer, it is proxied to the back end but the destination server may be other that the front end server that receivced i

DNS plays one of the most important roles in IT, there's no doubt about it. Especially when you have services hosted on public clouds or accessible on the internet. When troubleshooting issues with such services the DNS configuration and propagation should always be checked since any issues there would definately have an impact on the service. Although you can use the tools provided by your operating system such as nslookup, dig and Resolve-DNSName, it can be a bit complicated to get the right query. Fortunatelly, there are websites out there that can help you by providing a frienly user interface. The website I'm using the most is Dig Web Interface , let's take a quick tour. This site has a minimal design, with a textbox to enter your hosts or IPs and a few options about the query and the name server to use: Let's go through some example queries. To search for the name servers of a zone, use the "NS" type: As you can see, my domain is hosted o