What is my IP address and how does it work? Can it be changed?
An IP address is a string of bits, typically represented as a set of four integers separated by dots in the case of IPv4. IPv6 addresses are represented as a set of hex values separated by colons. In either case, these representations are purely for readability by humans; all network equipment reads these addresses as a string of bits with different bits holding different purposes and values.
There are different types of IP addresses. There are publicly routable addresses that allow your computer/router to communicate with other addresses on the internet. There are also private addresses that are only routable on your private network. In the IPv4 address space, these private addresses are further divided into several classes, the most common being Class A (typically 10.0.0.0/8), Class B (typically 172.16.0.0/16), and Class C (typically 192.168.1.0/24). These are the type of addresses that are assigned by most home routers and usually defaults to the class C range. If this is the type of address you are referring to and you are attempting to configure your Cisco router, you likely need to enable the DHCP server so that it gives addresses to other clients on your network. You will need to assign a static address to the interface that the DHCP server will be operating from.
Can it change? That largely depends on how you got the address. If you are referring to private addresses, it can change regularly. Although, due to caching mechanisms it’s also possible for a device to keep the same address for a *very* long time. If you’re referring to a public address it’s also possible these will change, unless you are leasing address space from your ISP.
Most ISP’s allow you to lease addresses. If you lease an address from your ISP they will likely only setup the routes to your connection and leave it to you to properly configure your router with your proper address. In this case your (public) address would not change, although if you are using a router your private addresses assigned to various devices on your network *could* still change their private address.
It is possible to lease an IP and assign it directly to a device without a router.
In this case, the IP address for your device would not change, but this address could *only* be used by this one device. This is why the distinction between public and private addresses exist. Without private addresses the IPv4 address space would have been exhausted (all addresses would have been assigned) a long time ago, but with the use of private addresses, multiple devices can share the same public address.
