Bizarre iPerf3 Result

[Twitch]

Hey gang - anyone really good with iPerf? I'm getting a really bizarre result that appears to demonstrate that our circuit provider is throttling our speed over a site-to-site VPN connection. The connection is supposed to be 100 Mbps, with 1 Gbps within the network at either end. A screenshot of the iPerf3 result is below. Notice how it starts at 679 Mbps in our network, and then just plummets to roughly 30 Mbps over the site-to-site circuit. Repeated tests show the site-to-site circuit running in the teens on occasion.

The circuit provider claims we are not being throttled. I can't find anything in the Meraki gear on either end (MX100 and MX84) that would throttle the connection. We have had a network performance issue between these two plants for a while now, and repeated attempts to try and determine why have come back empty.

When I run the test over our new 100 Mbps VPLS circuit, I get an average of 94 Mbps end-to-end consistently.

Has anyone else seen similar results?

Thanks.

Twitch

This test is running from a domain controller at our other plant over the site-to-site to my workstation:

[PhilipDAth]

Are you able to plug a notebook directly into the Internet circuit at each end, so that everything is bypassed, and repeat the test?  This will give you the most conclusive result.

[Twitch]

@PhilipDAthGreat point. I'll have to try that during the upcoming downtime we have scheduled.

[PhilipDAth]

Also I would do both a UDP and a TCP test.  AutoVPN uses UDP mostly.

If there is no traffic shaping, you would expect them to get the same result.  If the results are different ...