How to troubleshoot network problems on Linux

These diagnostic tools help with connection problems:

Test the connection:
ping google.com – Checks whether there is an internet connection.
ping YOUR-SERVER-IP – Checks whether the server is reachable.

Test DNS resolution:
nslookup your-domain.com
dig your-domain.com

Show open ports:
sudo ss -tlnp – Shows all listening TCP ports.
sudo netstat -tlnp – Alternative (you may need sudo apt install net-tools).

Trace the route:
traceroute google.com – Shows the network path.
mtr google.com – Combines ping and traceroute (interactive).

Test bandwidth:
sudo apt install speedtest-cli
speedtest-cli

Show network interfaces:
ip addr show
ip route show

Tip: If you suspect a firewall problem, check the rules with sudo ufw status or sudo iptables -L -n.