This was encountered in a lab environment. Everything looked fine. Network ports all checked. Another existing windows client on the same subnet could even complete the TFTP download of the target smsboot\x64\wdsnbp.com file. Event logs indicated that the TFTP transfer began but then failed producing a an Event ID 4101 in the Deployment-Services-Diagnostics Admin log.
The Following Client failed TFTP Download:
Client IP: 10.0.3.13
Filename: smsboot\x64\wdsnbp.com
ErrorCode: 1460
File Size: 30832
Client Port: 2071
Server Port: 53574
Variable Window: false
This post suggested a block size change which resolved the issue after a WDS service restart.
This older article also refers to block size changing
https://support.microsoft.com/en-gb/help/975710/operating-system-deployment-over-a-network-by-using-wds-fails-in-windo
Changing the block size is achieved in the registry as follows
Location:HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\services\WDSServer\Providers\WDSTFTP
Name: MaximumBlockSize
Type: (REG_DWORD)
Value range: 512–1456
Base: (Decimal)
Setting a 512 value resolved the problem.
The value can also be changed in the WDS applet in Maximum Block Size on the TFTP tab of the WDS server properties.
SCCM 2012 2002 (Microsoft Endpoint configuration manager) on Windows Server 2019
