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I have two networks connected trough a VPN connection (Wireguard). Let's call them Site A and Site B.

The VPN connection is working, routes are set, and all machines from Site A and Site B can ping each other without any issue. Accessing a webpage in Site B from Site A used to work until recently (Sometimes it works, and then suddenly stops again), accessing any webpage on Site B yields a ever loading white webpage that never ends loading.

The problem shows up when bigger chunks of data needs to be transferred like for example an image of a webpage, or a bigger HTML file (1KB+), the response never arrives completely.

Very small pages do load. And in every case the server sees that there is a request made, but no answer arrives to the client.

Running IPERF3 shows the issue in more detail:

SITE A:

root@aligator:~# iperf3 -c 192.168.178.254 -R
Connecting to host 192.168.178.254, port 5201
Reverse mode, remote host 192.168.178.254 is sending
[  4] local 192.168.250.254 port 53480 connected to 192.168.178.254 port 5201
[ ID] Interval           Transfer     Bandwidth
[  4]   0.00-1.00   sec  1.03 MBytes  8.64 Mbits/sec
[  4]   1.00-2.00   sec  1.17 MBytes  9.80 Mbits/sec
[  4]   2.00-3.00   sec   870 KBytes  7.12 Mbits/sec
[  4]   3.00-4.00   sec   477 KBytes  3.91 Mbits/sec
[  4]   4.00-5.00   sec   325 KBytes  2.66 Mbits/sec
[  4]   5.00-6.00   sec   407 KBytes  3.34 Mbits/sec
[  4]   6.00-7.00   sec   454 KBytes  3.72 Mbits/sec
[  4]   7.00-8.00   sec   556 KBytes  4.55 Mbits/sec
[  4]   8.00-9.00   sec   633 KBytes  5.19 Mbits/sec
[  4]   9.00-10.00  sec   442 KBytes  3.62 Mbits/sec
- - - - - - - - - - - - - - - - - - - - - - - - -
[ ID] Interval           Transfer     Bandwidth       Retr
[  4]   0.00-10.00  sec  7.03 MBytes  5.90 Mbits/sec   25             sender
[  4]   0.00-10.00  sec  6.39 MBytes  5.36 Mbits/sec                  receiver

iperf Done.
root@aligator:~# iperf3 -c 192.168.178.254
Connecting to host 192.168.178.254, port 5201
[  4] local 192.168.250.254 port 53484 connected to 192.168.178.254 port 5201
[ ID] Interval           Transfer     Bandwidth       Retr  Cwnd
[  4]   0.00-1.00   sec  88.2 KBytes   721 Kbits/sec    1   1.34 KBytes
[  4]   1.00-2.00   sec  0.00 Bytes  0.00 bits/sec    1   1.34 KBytes
[  4]   2.00-3.00   sec  0.00 Bytes  0.00 bits/sec    1   1.34 KBytes
[  4]   3.00-4.00   sec  0.00 Bytes  0.00 bits/sec    0   1.34 KBytes
[  4]   4.00-5.00   sec  0.00 Bytes  0.00 bits/sec    1   1.34 KBytes
[  4]   5.00-6.00   sec  0.00 Bytes  0.00 bits/sec    0   1.34 KBytes
[  4]   6.00-7.00   sec  0.00 Bytes  0.00 bits/sec    0   1.34 KBytes
[  4]   7.00-8.00   sec  0.00 Bytes  0.00 bits/sec    0   1.34 KBytes
[  4]   8.00-9.00   sec  0.00 Bytes  0.00 bits/sec    0   1.34 KBytes
[  4]   9.00-10.00  sec  0.00 Bytes  0.00 bits/sec    1   1.34 KBytes
- - - - - - - - - - - - - - - - - - - - - - - - -
[ ID] Interval           Transfer     Bandwidth       Retr
[  4]   0.00-10.00  sec  88.2 KBytes  72.2 Kbits/sec    5             sender
[  4]   0.00-10.00  sec  0.00 Bytes  0.00 bits/sec                  receiver

iperf Done.

SITE B:

root@baloon:~# iperf3 -s
-----------------------------------------------------------
Server listening on 5201
-----------------------------------------------------------
Accepted connection from 192.168.250.254, port 53506
[  5] local 192.168.178.254 port 5201 connected to 192.168.250.254 port 53508
[ ID] Interval           Transfer     Bandwidth       Retr  Cwnd
[  5]   0.00-1.00   sec   688 KBytes  5.63 Mbits/sec    3   58.8 KBytes
[  5]   1.00-2.00   sec   541 KBytes  4.43 Mbits/sec    3   33.4 KBytes
[  5]   2.00-3.00   sec   502 KBytes  4.12 Mbits/sec    0   41.4 KBytes
[  5]   3.00-4.00   sec   251 KBytes  2.06 Mbits/sec    2   37.4 KBytes
[  5]   4.00-5.00   sec   502 KBytes  4.12 Mbits/sec    0   41.4 KBytes
[  5]   5.00-6.00   sec   377 KBytes  3.09 Mbits/sec    0   48.1 KBytes
[  5]   6.00-7.00   sec   502 KBytes  4.12 Mbits/sec    1   41.4 KBytes
[  5]   7.00-8.00   sec   377 KBytes  3.09 Mbits/sec    1   36.1 KBytes
[  5]   8.00-9.00   sec   502 KBytes  4.12 Mbits/sec    1   28.1 KBytes
[  5]   9.00-10.00  sec   251 KBytes  2.06 Mbits/sec    0   34.7 KBytes
[  5]  10.00-10.09  sec   126 KBytes  11.4 Mbits/sec    0   34.7 KBytes
- - - - - - - - - - - - - - - - - - - - - - - - -
[ ID] Interval           Transfer     Bandwidth       Retr
[  5]   0.00-10.09  sec  4.51 MBytes  3.75 Mbits/sec   11             sender
[  5]   0.00-10.09  sec  0.00 Bytes  0.00 bits/sec                  receiver
-----------------------------------------------------------
Server listening on 5201
-----------------------------------------------------------
Accepted connection from 192.168.250.254, port 53510
[  5] local 192.168.178.254 port 5201 connected to 192.168.250.254 port 53512
[ ID] Interval           Transfer     Bandwidth
[  5]   0.00-1.00   sec  0.00 Bytes  0.00 bits/sec
[  5]   1.00-2.00   sec  0.00 Bytes  0.00 bits/sec
[  5]   2.00-3.00   sec  0.00 Bytes  0.00 bits/sec
[  5]   3.00-4.00   sec  0.00 Bytes  0.00 bits/sec
[  5]   4.00-5.00   sec  0.00 Bytes  0.00 bits/sec
[  5]   5.00-6.00   sec  0.00 Bytes  0.00 bits/sec
[  5]   6.00-7.00   sec  0.00 Bytes  0.00 bits/sec
[  5]   7.00-8.00   sec  0.00 Bytes  0.00 bits/sec
[  5]   8.00-9.00   sec  0.00 Bytes  0.00 bits/sec
[  5]   9.00-10.00  sec  0.00 Bytes  0.00 bits/sec
[  5]  10.00-10.09  sec  0.00 Bytes  0.00 bits/sec
- - - - - - - - - - - - - - - - - - - - - - - - -
[ ID] Interval           Transfer     Bandwidth
[  5]   0.00-10.09  sec  0.00 Bytes  0.00 bits/sec                  sender
[  5]   0.00-10.09  sec  0.00 Bytes  0.00 bits/sec                  receiver
-----------------------------------------------------------
Server listening on 5201
-----------------------------------------------------------

So in both test runs both server and client see that there is a new request, but no data is sent from SITE B to SITE A (At least not more than some bytes).

Also, this issue seems to randomly disappear and appear again, so there are times that communication in both directions work fine for a while, and then collapse again. But Pinging always works (And SSH usually too).

I know that this might not be enough information to solve the issue, but I don't know where to even start to search for the issue (Routing, VPN, Unreliable network?). Can anybody point out what kind of issue could generate this kind of behaviour? What would be the best place to start looking for the cause?

  • It used to always work? Does ping continue to work when the TCP connections start failing? Does udp always work? – rogerdpack May 9 at 23:04
  • @rogerdpack. The setup is recent, it has been running 2 or 3 weeks before without having noticed any kind of issues. Now it seems like the the connection works only a few seconds after restarting all devices (Client and Server) but shortly after it again starts failing. I tested with UDP in Iperfv3 with the same result. – Robert Koszewski May 13 at 17:46

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