This option specifies the protocol value that smbd 8 will return to a client, informing the client of the largest size that may be sent to the server by a single SMB2 write call. The maximum is 8388608 bytes (8MiB), which is the same as a Windows Server 2012 r2. Please note that the default is 8MiB, but it's limit is based on the smb2 dialect (64KiB for SMB == 2.0, 8MiB for SMB => 2.1 with LargeMTU). Large MTU is not supported over NBT (tcp port 139). smb2 max read smb2 max trans 8388608