Common network troubleshooting commands


When trying to diagnose a problem accessing a website or server there are a number of command prompt commands that can be used to determine what may be wrong. The output from these commands can often be useful when speaking with technical support to report a problem so try to run these commands before reporting a site or server down.

Opening a command prompt

In Microsoft Windows open the start menu and type "Command" to search for the command prompt, click the black and white icon that appears. On older versions of Windows you may also be able to click "Run" in the start menu and run the command "cmd"

In Linux and macOS you can open a command prompt, or terminal, but using the search tool or Spotlight on macOS to search for "Terminal"

Ping

Pinging a server is the most basic way to check whether it is online and accessible. A ping is a small packet of data called "echo" that a receiving server responds to with a "reply" - if no reply is received then communication at it's most basic level isn't functioning. To ping a server issue the following command, replacing the website or server name with the one you want to test, on any operating system from the command prompt or terminal:
ping freethought-internet.co.uk
You should output like this if all is working properly:
PING freethought-internet.co.uk (194.110.243.242): 56 data bytes
64 bytes from 194.110.243.242: icmp_seq=0 ttl=47 time=17.021 ms
64 bytes from 194.110.243.242: icmp_seq=1 ttl=47 time=17.103 ms
64 bytes from 194.110.243.242: icmp_seq=2 ttl=47 time=18.832 ms
64 bytes from 194.110.243.242: icmp_seq=3 ttl=47 time=18.420 ms
^C

--- freethought-internet.co.uk ping statistics ---
4 packets transmitted, 4 packets received, 0.0% packet loss
round-trip min/avg/max/stddev = 17.021/17.844/18.832/0.796 ms
Once started in Linux and macOS you may have to manually stop the command running by pressing Ctrl+C

If you receive replies then that means everything is working properly and you can communicate, if however you receive a response mentioning timeout or anything other than a reply message then communication is not possible and the server may well be down, or some other problem exists which further checks detail below may reveal.

If you don't receive replies and you used a human friendly domain name to ping such as freethought-internet.co.uk then try again but instead ping an IP address, if it can ping the IP address then you know that something is wrong with your DNS which is what translates domain names to IP addresses. You can test DNS with nslookup.


Testing DNS with nslookup

When testing with ping it is natural to at first test with a human readable website address or hostname, however the actual ping will use the server IP address. Computers translate website addresses and hostnames to IP addresses with a service called DNS. If DNS is malfunctioning then a ping would fail as it would not be able to determine the IP address to ping, what's more, browsing to that website would not work if DNS was malfunctioning.
To test if DNS is working issue the following command, replacing the address with the site you want to test:
nslookup freethought-internet.co.uk
If DNS is working you should get something similar to the following output:
Server:10.10.2.1
Address:10.10.2.1#53


Non-authoritative answer:
Name:freethought-internet.co.uk
Address: 194.110.243.242
If you see anything different such as the following then there is likely a problem:
** server can't find freethought-internet.co.uk: NXDOMAIN
An error like the one above indicates that either the DNS for your website is not functioning, in which case you should speak with Freethought support, or the DNS on your computer is just not functioning at all. Without functioning DNS then you won't be able to access your website, or any website come to that. You could re-run the above test but use a popular website unlikely to be having problems like bbc.co.uk or google.com - if they also give an error then you know that your DNS is broken in general and it isn't a problem with your Freethought service.

Traceroute

Another useful command when testing connectivity to a website or server is to run a traceroute. Where a ping timesout and DNS issues are not the problem then it could be that the connectivity problem exists with your ISP's network or somewhere else between your computer and the server where your website or server is located. A traceroute "traces" the route between your computer and the site you are testing, where the trace stops is where the problem exists.

To run a traceroute use the following command, replacing the address with the one you want to test:
traceroute freethought-internet.co.uk
On Microsoft Windows the command is slightly different:
tracert freethought-internet.co.uk
The output regardless of operating system will look like the following:
traceroute to freethought-internet.co.uk (194.110.243.242), 64 hops max, 52 byte packets

 1  10.10.2.1 (10.10.2.1)  1.560 ms  1.093 ms  0.680 ms

 2  * * *

 3  leed-core-2a-xe-113-0.network.virginmedia.net (81.111.190.17)  10.411 ms  10.282 ms  9.534 ms

 4  * * *

 5  * * *

 6  * * *

 7  * * *

 8  nrth-ic-1-ae1-0.network.virginmedia.net (62.254.42.218)  30.453 ms  15.338 ms  12.811 ms

 9  m674-mp2.cvx1-b.lis.dial.ntli.net (62.254.42.162)  17.996 ms  18.910 ms  17.363 ms

10  213.46.174.46 (213.46.174.46)  18.106 ms  17.311 ms  19.483 ms

11  ge-0-0-3.ldex1-rt1.uk.as41000.net (149.11.22.186)  23.251 ms  18.103 ms  17.245 ms

12  0.ge-0-0-0.thn-csw1.uk.as41000.net (176.74.23.197)  19.270 ms  19.405 ms  19.426 ms

13  0.ge-0-0-46.ldex1-csw1.uk.as41000.net (176.74.23.194)  20.220 ms  23.978 ms  24.736 ms

14  ldex1-web3.uk.fi.net.uk (194.110.243.242)  19.644 ms  21.252 ms  17.811 ms

Asterisks indicate a timeout, depending on where those asterisks are in the trace determines whether there is a problem. It is quite common to have asterisks in the middle of traces where some ISPs block ping to some of their network devices, asterisks at the end of a trace before reaching the service you are testing are the problem we're looking for. If in a traceroute it stops at an address that looks like part of your ISPs network then it may well be that your ISP is having problems currently, wait a while longer and try again.

Diagnosing a traceroute can be complicated and vary depending on what you are testing, if you have a traceroute output that you think shows a problem then email the output to Freethought support for assistance.

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