Your DHCP server must be in only one VLAN

Recently, we have made a major upgrade of the network infrastructure for one customer. We replaced the old switches and introduced the complete VLAN infrastructure. At the end of the day, everything seemed to be good.

Then, after two days, DUDE started to raise alarms related to DHCP service. We received a bunch of e-mails related to an empty DHCP pool. It was a mystery how this DHCP pool emptied when there are only 10 workstations and this happened during a public holiday when the offices were empty. Continue reading

Advertisements

Duplicate V3 extension in a X.509 certificate

Recently, I got a report that one application can’t connect to the Exchange server. The error message was:

Exchange server error: The request failed. javax.net.ssl.SSLProtocolException: java.io.IOException: Duplicate extensions not allowed.

The first Google search revealed to me that this error message is related to the error inside the SSL certificate and the java based library can’t override such situation. Continue reading

Advanced disk repairing option in Windows 8 and later

A few months ago, I encountered a problem with one USB hard disk. Whenever it was attached to any PC, Windows will prompt that volume has errors. As always, we click on Scan and Fix option expecting that that would do the job.

This disk was one of a kind and now you can read about it. I tried a few times to repair it. Every time, the disk check passed and all was fine, until I again needed to reconnect the disk. Then the story repeated. Continue reading

Reading file details on the Windows Core system

If you want to view a file details in Windows with GUI, you need to right-click on the file in Explorer, select Properties from the context menu and then click on the Details tab. Easy.

Can you do the same task using only the command line? With a little magic and a few mighty tricks you can do that, too.

Continue reading

Windows Update failed with the error code 8024402C

I have a very strict policy that servers must not access the Net. If a server needs to be accessible from the Net, it will be placed in the DMZ zone with very rigid firewall rules. To update all servers, I need to implement the WSUS server in the local network.

I never let servers update automatically. Rather, I let them notify me about available updates and then I will manually run an installation process.

Continue reading

Installation of IE11 failed with code 9C47

Recently, I found that one of the servers doesn’t have IE11. I was surprised by that, but OK. I never use IE (or any other browser) on any server. Additionally, most of the servers don’t even have the default gateway address.

I ran Windows update, it started to work….

Continue reading