Keith Smith - My Blog

event id 5807

Tuesday, March 27, 2018 - by Keith A. Smith

I recently encountered a rare event log entry event id 5807

During the past 4.22 hours there have been 24 connections to this Domain Controller from client machines whose IP addresses don't map to any of the existing sites in the enterprise. Those clients, therefore, have undefined sites and may connect to any Domain Controller including those that are in far distant locations from the clients. A client's site is determined by the mapping of its subnet to one of the existing sites. To move the above clients to one of the sites, please consider creating subnet object(s) covering the above IP addresses with mapping to one of the existing sites.

The names and IP addresses of the clients in question have been logged on this computer in the following log file '%SystemRoot%\debug\netlogon.log' and, potentially, in the log file '%SystemRoot%\debug\netlogon.bak' created if the former log becomes full. The log(s) may contain additional unrelated debugging information. To filter out the needed information, please search for lines which contain text 'NO_CLIENT_SITE:'. The first word after this string is the client name and the second word is the client IP address. The maximum size of the log(s) is controlled by the following registry DWORD value 'HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Netlogon\Parameters\LogFileMaxSize'; the default is 20000000 bytes.  The current maximum size is 20000000 bytes.  To set a different maximum size, create the above registry value and set the desired maximum size in bytes.

After doing a search for netlogon.log and taking a closer look at the netlogon.log file, I noticed that it doesn’t record the year of each entry, just the day and month.  I scrolling down to the bottom and all the most recent entries, I noticed that the ip address range had not been defined in AD Sites and Services.  The IP’s were from laptops connecting through the VPN which was assigning a completely different subnet,  so I just added the VPN subnet and everything was fine after that.

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