Linux 101 : Network layers and their respective troubleshooting tools - ip link, traceroute, nslookup, ... -

Below is a simplified diagram of the different network layers:

To get information about the link layer - Hardware -, we would use the below command to check if the interface is running:

We could turn on the interface - if it is down - using the below command:

Another command for checking interfaces would be:

For layer 2, which is concerned with MAC addresses, we could check the ARP table using the below command:

To delete a wrong entry from the ARP table, we could use the below command:

The layer 3 handles the IP addressing. For that layer, we could use the below command to check the IP routing information:

We could also use the "traceroute" command to check the route to a specific destination:

Or check our DNS using the below command:

We can check if the remote host is up and running, using the below command:

The TCP/UDP layers could be checked using the below commands.

For TCP sockets, we would use:

For UDP sockets, we would use the below:

To display the listening sockets we could use:


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