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Troubleshooting

Reviewed on 18 August 2021Published on 20 August 2021

Running network tests

To diagnose a network issue, you can perform different tests.

MTR test

An MTR test combines the functions of traceroute and ping on all points between two machines.

When running an MTR test, it is important to do it in both directions:

  • From the server to the IP of your connection
  • From your connection to the server

On Linux

You have to check that the mtr packet is installed.

sudo apt-get install mtr

or

sudo yum install mtr

On Windows

You have to install WinMTR on your server: https://sourceforge.net/projects/winmtr/

Once you have downloaded it, extract the archive and run the executable.

Enter the target (IP) of your test in the Host textbox, then click on Start. Wait one or two minutes before you stop the test. You can then make a screenshot or export the result with the functions of the software.

Example of MTR between an Online.net server and free.fr:

root@163-172-30-2:~# mtr --report free.fr
Start: Sun May 1 16:23:57 2016
HOST: 163-172-30-2 Loss% Snt Last Avg Best Wrst StDev
1.|-- 163-172-30-1.rev.poneytel 0.0% 10 0.5 0.5 0.4 0.5 0.0
2.|-- 195.154.1.248 0.0% 10 1.6 1.0 0.9 1.6 0.0
3.|-- 195.154.1.254 0.0% 10 1.2 1.4 1.2 2.6 0.3
4.|-- th2-crs16-1-be1503-t.intf 0.0% 10 1.3 1.3 1.1 1.4 0.0
5.|-- p11-crs16-1-be1001.intf.r 0.0% 10 4.5 3.0 1.4 4.5 0.7
6.|-- p11-9k-1-be1000.intf.rout 0.0% 10 1.5 2.1 1.4 3.5 0.6
7.|-- bzn-9k-2-sys-be2001.intf. 0.0% 10 1.7 1.8 1.6 2.8 0.0
8.|-- www.free.fr 0.0% 10 1.2 1.2 1.2 1.2 0.0

The results show:

Loss%
The percentage of lost packets
Snt
The number of packets sent during the test (here 10)
Last
The latency of the last packet sent between two points
Avg
Average latency for all packets sent between two points
Best
Latency of the best result
Wrst
Latency of the worst result

IPERF test

With an IPERF test you can check the available bandwidth of your server.

The iperf server ping.online.net has several ports available (5200-5209). If the server is busy on the default port, you can specify another port using the -p flag, for example: -p 5203 (5204, 5205, etc.).

On Linux

If iperf is not yet installed on your server, you can install it with the following command:

sudo apt-get install iperf3

or

yum apt-get install iperf3

Then launch the test:

root@163-172-30-2:~# iperf3 -c ping.online.net -R
------------------------------------------------------------
Client connecting to ping.online.net, TCP port 5001
TCP window size: 85.0 KByte (default)
------------------------------------------------------------
[ 3] local 163.172.30.2 port 36490 connected with 62.210.18.40 port 5001
[ ID] Interval Transfer Bandwidth
[ 3] 0.0-10.0 sec 1.10 GBytes 943 Mbits/sec
If your server is located at Amsterdam execute: root@163-172-30-2:~# iperf3 -c ping-ams1.online.net -R

On Windows

  1. Download the tool here.

  2. Choose the latest version and download the file.

  3. Extract the file.

  4. Open a terminal and run the following command:

\iperf3.exe -c ping.online.net -p 5203

The results show:

Interval
Sampling interval in seconds
Transfer
Amount of data transferred during the test
Bandwidth
Available bandwidth of your server

If your server’s network port is off

Sometimes when you change the mode of your dedicated server from normal to rescue mode during the reboot of a server, you may see the following error message in your console:

Important:

Your server’s network port is off. If you just asked for a server reboot, or to boot in rescue or test mode, this message will only be displayed for a few seconds. Otherwise, our network equipment may be on protective mode due to non-authorized traffic. In this case, please ask the support team to unlock your server.

If this message is visible for a longer period or cycles every 5 minutes, it means your server is either distributing unauthorized traffic in the style of DHCP, distributing a MAC address that is not assigned to the server, ARP requests, too many requests per second in sending or receiving on your server.

If you continue to see this message, empty the cache of your browser as the old page may be kept in it. Alternatively, you can reload the page several times until the message disappears.

Important:

When setting up the WAN interface on a PfSense firewall you should disable auto-configuration, as it might cause an IPv6 packet flood shutting down your server’s network port. If your network ports do not become available after a few minutes, you need to contact the support.