Detect network issues from your pc to a remote url
Suppose you see that a website, or a URL, that seems to be unaccessible.
The first thing to do is to check if the website is down just for you or for the whole universe. There are many websites that do this, the one I discovered recently is Uptrends.
By putting a url in uptrends you can see how long a resource will take to load from a bunch of locations in the world:
Oh no! There's an issue in Europe!
Another check you can do is for proper hackers ®. Launch this command from bash:
$ sudo mtr -rwc 50 <url>
The result is a very nice list of all hops made by data from our PC to the remote host
➜ ~ sudo mtr -rwc 50 michelenasti.com
[sudo] password di musikele:
Start: 2019-08-02T10:27:39+0200
HOST: musikele-XPS-15-9560 Loss% Snt Last Avg Best Wrst StDev
1.|-- _gateway 0.0% 50 2.7 2.2 1.9 4.2 0.4
2.|-- ??? 100.0 50 0.0 0.0 0.0 0.0 0.0
3.|-- 172.18.18.108 0.0% 50 10.6 10.7 8.5 16.8 1.5
4.|-- 172.18.19.226 56.0% 50 11.7 11.3 9.0 30.4 4.6
5.|-- 172.19.177.38 0.0% 50 16.5 16.9 15.6 19.6 0.7
6.|-- 172.19.177.2 0.0% 50 27.4 27.8 24.6 69.4 8.6
7.|-- etrunk49.milano50.mil.seabone.net 52.0% 50 28.2 28.3 26.6 40.6 2.9
8.|-- et9-1-0.ashburn2.ash.seabone.net 0.0% 50 122.1 121.0 119.1 129.5 2.0
9.|-- cloudflare.ashburn2.ash.seabone.net 0.0% 50 128.3 133.4 125.5 216.4 14.6
10.|-- 104.28.13.252 0.0% 50 124.4 124.8 123.5 126.3 0.6
➜ ~ mtr stands for My TraceRoute and combines ping with traceroute. It gives a lot of information about the routers crossed during the path to the destination.
One may think that there are some errors in the upper report, however you should have in mind that many routers are configured to delete ICMP packets (the ones used by mtr, or by ping) or to slow them down for quality assurance.
I really suggest you to read this article from Linode that explains almost everything you may want to know and it's very easy to follow.
Enjoy your networking!