In an AD domain with Windows Server 2008 R2 DCs users are complaining about delays in the bootup process of the clients. The group policy log reveals that the client is waiting ~ 20-50 seconds for "the network subsystem":

Event 5322, GroupPolicy

Group policy waited for 29687 milliseconds for the network subsystem at computer boot.

This appears to be domain-specific as machines joining a different domain from the same network do not experience any delays and Event 5322 reports <1000 ms wait times at startup. It happens on virtual and physical machines alike, so it does not look like a hardware- or driver-related issue.

Further investigation has shown that the client is taking its time before issuing DHCP requests. In the network traces, I can see IPv6 router solicitations and multicast DNS name registrations as soon as the network driver is loaded and the network connection is reported "up" in the event log (e1cexpress/36). Yet, the DHCPv4 client service seems to take another 15-50 seconds to start (Dhcp-Client/50036), so the IPv4 address remains unconfigured for a while.

The DHCP client's messages in the event log are succeeding the service start of the "Sophos Anti-Virus" service (Sophos AV 10.3 package), which I suspect to be the culprit - the DHCP client service dependencies include the TDI Support driver which might be what Sophos is using to intercept network traffic:

Network Location Awareness seems to break at startup as a side-effect, I see that off-site DCs are contacted due to what seems like a race condition between the GP client and the DHCP client / NLA service startup. I could set the Group Policy Client service to depend on NLA, yet this still would not eliminate the delay. Also, I am not all that sure that this is a good idea.

Is there a known resolution which would eliminate the startup delay?