How to check your network connections on Linux

How to check your network connections on Linux

The ip command has a lot to tell you about the configuration and state of your network connections, but what do all those words and numbers mean? Let’s take a deep dive in and see what all the displayed values are trying to tell you.

When you use the ip a (or ip addr) command to get information on all the network interfaces on your system, you’re going to see something like this:

$ ip a
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN group default qlen 1000 link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00 inet scope host lo valid_lft forever preferred_lft forever inet6 ::1/128 scope host valid_lft forever preferred_lft forever
2: enp0s25: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP group default qlen 1000 link/ether 00:1e:4f:c8:43:fc brd ff:ff:ff:ff:ff:ff inet brd scope global dynamic enp0s25 valid_lft 57295sec preferred_lft 57295sec inet6 fe80::2c8e:1de0:a862:14fd/64 scope link valid_lft forever preferred_lft forever

The two interfaces on this system — the loopback (lo) and network (enp0s25) — are displayed along with a lot of stats. The “lo” interface is clearly the loopback. We can see the loopback IPv4 address ( and the loopback IPv6 (::1) in the listing. The normal network interface is more interesting.

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