Archive for the ‘Server’ Category

Resolving nslookup: Default Server Unknown

Thursday, March 7th, 2013

All windows installations include a command-line network utility that allows the user to make queries against the DNS server registered on the (domain) network. Typically a user enters the name of a workstation or IP address and is returned either the IP or hostname depending on what is initially entered.

If the DNS server on the domain controller has not been fully configured then the nslookup utility may return “default server unknown” when running queries. This simply means that the DNS server does not have any information to determine the hostname of the IP. To fix this problem, the DNS server needs to be configured for reverse DNS lookups. Reverse DNS lookups allow the DNS server to correlate the correct hostname for a given IP. In some configurations the DNS server is only configured to do forward lookup zones, which correlate hostnames to the corresponding IP addresses.

DNS Reverse Lookup ZoneTo fix the issue, go to the DNS control panel on the domain controller. Right click the Reverse Lookup Zone tree and select “New Zone.” Simply follow the guided wizard and ensure the reverse zone is setup for the same subnet as the forward lookup zone.

Once this has been configured, the DNS server will begin creating Pointer Records (PTR) that will enable nslookup to successfully make queries that return the proper data instead of “unknown.”

Computer Monitoring Error: The Mystery Continues

Tuesday, March 5th, 2013

computer monitoring errorSince Windows Home Server 2011, the “Computer Monitoring Error” alert provided in the Alert Viewer on the client Launchpad/server dashboard has been incredibly frustrating and unexplainable. Sometimes the computer monitoring error was caused by a disabled Windows Firewall, while other times the error would appear and disappear on a rotating basis.

After thinking I’d never bump into the issue again, a new installation of Server 2012 Essentials proved otherwise. After connecting one of the client systems to the 2012 Essentials domain, it wasn’t long before a new Computer Monitoring Error appeared. In Server 2012 Essentials however, the server’s event viewer provided additional information:

Warning Alert: !Warning is raised at COMPUTERNAME.Computer monitoring error. Can only partially assess the health of this computer. The failing components are: DeviceProviderReporting!DomainJoinStatusInfo. <AdditionalInfo> Logon failure: unknown user name or bad password.

After further investigation, it would appear the 2012 Essentials server logs several failed network login attempts whenever the computer is booted and connects to the network. The security audits are logged with an event ID of 4625, and describe a “NULL SID” failing to login with the computer that is causing the source of the warning.

After taking several steps to try and identify why this authorization is failing, and why the server does not have the right connections to connect, I must admit that I have found nothing – I’m stuck. I have narrowed it down to being an Active Directory, Certificate, or NTLM issue of some sort but am still attempting to provide a solution for others who may be experiencing a similar issue. Unfortunately Microsoft has not updated the help documentation for this error message and there are still too many leads to pinpoint. Hopefully the answer will reveal itself soon.

Windows Server RRAS: Change Initial DHCP Reservation Size

Saturday, March 2nd, 2013

Woods Networks¬†offered a great solution to a common pester in Server 2003-2012. The Routing and Remote Access feature that allows for VPN connections to the target domain takes reservations in the DHCP server in blocks of 10. It would occasionally steal other computers’ IP addresses and cause conflicts on the network from consuming all of the lower IP range. Although there is a built in feature to set a static range, doing so prevented full connectivity to the subnet that the DHCP server and clients resided on. The following simple registry edit will allow you to change the default reservation size.


Value Name: InitialAddressPoolSize

Data Type: REG_DWORD

Default: 10

Computer Limbo