VPN consuming double bandwidth downstream?

[PhilB]

I have Win 8.1 64bit client build 9599 and a Win10 64bit client build 9599 behind NAT connecting to a 2008 64bit server 9599 with no NAT

The server has one Virtual Hub, bridged to the inside LAN interface.

I have noticed that downloading (to the client) is suddenly extremely variable (it used to work fine - I could stream HD video over SMB, etc). Upon closer inspection I have noticed I am getting, at best, half throughput (eg; using speedtest.net through the VPN yields 15mbps peak where my connection at home is 30mbps), and SMB performance is terrible.

However, if I check the task manager in windows, the physical interface shows it is receiving ~30-32mbps of traffic.

Absurdly, upload speed is still fine - 30-32mbps of physical interface traffic ~= 30mbps of throughput on the VPN

Both the server and the clients have been rebooted since this started.

I tried reducing the number of connections in case there was some weird issue with traffic being sent twice down multiple connections, but exactly the same behaviour is seen with 1 connection.

How do I begin to troubleshoot this?

I've attached the server configuration; as you can see, it's pretty basic.

[PhilB]

This is still happening. 100mbps pipe, 91mbps consumed, but only ~43mbps payload data.

Upstream won't go much faster than around 35mbps still, though, which doesn't make much sense to me, but at least when it's doing that, it's only consuming ~35-37mbps on the wire.

This is on a different client machine (now w10 64bit, previously w7 64bit). Server (w2008 64bit) and client software now both 4.21 9613.

Nobody else is seeing this?

[thisjun]

Try to capture packets on virtual NIC of client side.