We have three sites and a new server colocation facility that we are in the process of bringing online. We have several WDS servers at each site. We are moving servers from the smallest site to the colocation facility. The colocation facility connects to our network at our main location via site-to-site link with Cisco ASA firewalls at either end. All traffic is allowed, and routes correctly. The link between the sites is 400Mbps. I can do a file transfer via SMB or iperf and easily get over 200Mbps. Active Directory, Group Policy, and DFS Replication sync over the connection as fast as ever. Latency is 7-8ms. I have set up DHCP to point the PXE clients at the WDS server (Windows Server 2016) at the colocation facility. They are able to PXE boot and the entire process proceeds without failure, but the "Loading windows" screen with the progress bar above the IP address takes a really long time. When there is no other traffic to this server, I can check Task Manager and see it almost hard-limited to 5-6Mbps the entire time. This happens with our physical clients (several different models of HP EliteDesk desktops that work fine with local WDS servers) and Hyper-V virtual machines. Neither Cisco ASA firewall seems to be particularly overloaded during this process (RAM/CPU).


try to set/change the "Maximum Blocksize" (depended on your MTU?) and also "Variable Window Extension"

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  • My TFTB tab looks just like that, with a 0 max size and the Variable Window Extension box checked. What should the size be? – Sam Lewis Apr 19 at 14:27
  • As I sayd, I would check on those options. On the picture you find only the defaults. I think block size needs to be smaller than your MTU. Try also to remove Variable Window Extension. – Thomas Apr 21 at 0:17

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