How to Find Out If My IP Address Is Static or Dynamic in Linux?

The easiest way to determine if your external IP address is static is to do the following:

Write down the address.
Restart your router.
Check your external IP address again, and compare it. If it has changed, you have a dynamic external IP address. If it has not changed, you may have a static IP address.

How to Check an IP Address

o get the depth information of your network interfaces like IP Address, MAC Address information, use the following command as shown below.

# ip addr show
$ sudo ip addr show
Sample Output

1: lo: mtu 16436 qdisc noqueue state UNKNOWN
link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
inet 127.0.0.1/8 scope host lo
inet6 ::1/128 scope host
valid_lft forever preferred_lft forever
2: eth0: mtu 1500 qdisc pfifo_fast state UNKNOWN qlen 1000
link/ether 00:0c:29:28:fd:4c brd ff:ff:ff:ff:ff:ff
inet 192.168.50.2/24 brd 192.168.50.255 scope global eth0
inet6 fe80::20c:29ff:fe28:fd4c/64 scope link
valid_lft forever preferred_lft forever
3: eth1: mtu 1500 qdisc pfifo_fast state UNKNOWN qlen 1000
link/ether 00:0c:29:28:fd:56 brd ff:ff:ff:ff:ff:ff
inet 192.168.50.5/24 scope global eth1
inet6 fe80::20c:29ff:fe28:fd56/64 scope link
valid_lft forever preferred_lft forever
Execute the following command from a terminal:

#cat /etc/network/interfaces
If your internal IP address is set as dynamic, it should contain something along the lines of

iface eth0 inet dhcp
And if it is static, it will contain

iface eth0 inet static