Linux · Network Diagnostics

You want a list of which ports your own server is listening on — and separately, which connections are currently live. What single command covers both, and how do the options change?

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More in Network Diagnostics

You want a quick look at the IP addresses under which a Linux box is reachable, but plain hostname only prints the name. Which invocation filters out the relevant addresses, and what is easy to type wrong?

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Modern Linux names an Ethernet port something like enp0s31f6 instead of the old eth0. What does the ugly name buy you that eth0 didn't?

In ip link output each interface has a 12-hex-digit value after link/ether. What is it and what does it identify?

ip addr on a working interface shows one global IPv6 plus an address starting with fe80. Why can't you reach the box from the internet on the fe80 one?

You run ping with just a target and it never stops. What is its default cadence, and how do you cap it at two probes?

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