Limited wireguard inbound traffic

Installing and Using OpenWrt
1

I am using OpenWrt on an Asus RT-AC88U. This router connected as client with cloud server using wireguard. My cloud has maximum throughput 100Mbps, I already tested this using iperf with public server. While my router ISP has maximum throughput about 150Mbps. Theoretically, connection between my router and cloud will be around 100Mbps. The problem is, this only applicable for outbound traffic (sending data from router to cloud). But, when I tried for inbound traffic (sending data from cloud to router), I don't even get above 10Mbps. I already reinstalled my cloud OS and reset my router before testing using iperf.

image
image1920×896 181 KB

I am not sure if this problem caused by hardware issue, since it's okay for outbound traffic. Is there a way to fix inbound problem?

Thanks in advance

2

My first guess would be your ISP throttling downlink traffic, especially during peak load time.

1 Like
3

I agree with @stangri.

Turn off your wireguard tunnel and run some speed tests with just the regular wan. What speeds do you get? What isp speed is promised based on your subscription with your isp (both up and down)?

4

My ISP promised for symmetrical bandwith for download and upload. Both of them up to 150Mbps. I reset my router (again, to be sure), then installed speedtestpp on my router. I ran the test and got:

  • Local server: 157.29 Mbit/s Download, 338.15 Mbit/s Upload
  • Singapore ISP server (cloud location): 175.82 Mbit/s Download, 251.84 Mbit/s Upload

I tried to use my cloud server speedtest, but it always return segmentation fault.

After that, I tried to use my cloud server as iperf server again. Since it's the one who has public IP, and wireguard not configured yet, so my router can connect to it. I just found out about -R flag, so it will simulate inbound traffic without using wireguard. Both of them got around 100Mbps.

5

You can try to lower the MTU of the WireGuard interface on both sides to e.g. 1280.
Note Max MTU is 1420 (or 1412 if you have PPPoE)

Furthermore enable MTU fix

6

image
image1920×849 173 KB

It actually got better, I am not sure if the cause is MTU or just some kind of deviation. But still far from theoretically possible bandwidth

If it's really because MTU, is there any reason for that?

7

Just undo the changes and retest then you know :slight_smile:

If it is MTU related you might try even lower

8

Tried to use default MTU, changed it to 500, back to 1280
It's wildly varied, at previous test (screenshot before), I can get 82Mbps. But now, not even touching 50Mbps.

9

After waiting and trying to tinkering using iperf3, somehow the problem fixed. Probably because of ISP issue.

10

This topic was automatically closed 10 days after the last reply. New replies are no longer allowed.