[German]I'm presenting a problem here in the blog that I came across while browsing Microsoft's Answers forums. On some systems, after upgrading to Windows 11 24H2, clients are unable to access a network, either via LAN or WLAN. The cause is a missing gateway entry that cannot be requested by the DHCP server due to a bug. It also does not help to enter the gateway manually, as it is lost again after the restart. An update from November 2024 seems to provide a remedy.
DHCP in Windows
The Dynamic Host Configuration Protocol (DHCP) is a communication protocol that is also used in Windows. A Windows client can use the protocol to obtain the IP address and network configuration from a DHCP server.
Windows 11 24H2: No network
In mid-October 2024, an administrator posted in the Microsoft Answers Forum for Windows 11 for IT Pros and reported problems in his environment in the thread Win11 24H2 – DHCP issue – no Gateway. He tried to update some clients to Windows 11 version 24H2 in test groups.
In doing so, he ran into a strange problem: Some of these Windows 11 24H2 clients did not get a network afterwards – neither via LAN nor via WLAN. The installation of Windows 11 24H2 was tested both via WSUS and directly with a USB stick.
The strange thing is that it doesn't affect all the clients that have been switched over, but the administrator ran into this problem with five machines in his test group. The same machines with Windows 11 23H2, on the other hand, showed no problems. It appeared that this problem was related to Windows 11 24H2, which was only released on October 1, 2024.
No DHCP gateway entry
An analysis of the affected clients very quickly revealed that the gateway was missing in the network configuration of the Windows 11 machines in question. The gateway can be entered manually and then everything works. But after a restart, the entry for the gateway was gone again.
The administrator wrote that the DHCP server was being used and that all settings had been checked and found to be OK. The configuration was complete, i.e. IP, mask, DNS server were entered correctly – only the gateway was missing in the network configuration. Attempts to reset the network stack using the console commands ipconfig /release or /renew did not help. Wireshark shows nothing conspicuous.
Another administrator confirmed this problem, and wrote that they observed it in their environment. The only thing that worked was to assign static IP addresses to the clients. Then the network worked fine, but when he removed the clients, that machine can no longer receive a domain IP address.
The person concerned suspected an authentication problem in a domain network, which also applied to the domain WiFi connection. He was able to connect to the guest WiFi network and gain Internet access. His cell phone used as a hotspot also enabled Internet access.
Another victim then analyzed the whole thing and used Wireshark to examine the DHCP traffic between a 23H2 computer and a 24H2 computer. In his environment, user class IDs are used to gateway the machines to prevent users from connecting personal devices. The upgrade to Windows 11 24H2 caused this client to send the DHCP discovery request without the user class information, resulting in the DHCP processing issues.
A solution was found
The discussion has been meandering in the MS Answers forum since mid-October 2024, with no further response from Microsoft. On December 5, 2024, a user contacted us and wrote that he had found a solution. The update KB5046617 for Windows 11 24H2, which was released on November 12, 2024, had fixed this problem in his environment. In fact, the support article states:
- [Internet connection] Fixed: A small number of devices cannot connect to the internet. This occurs when a DHCP server response has duplicate DHCP options. This stops IPv4 connections on certain networks.
Perhaps it will help if someone from the readership is affected by this problem in a corporate environment.
