Someone at my office recently asked me why their wireless routers always have a default IP address of 192.168.0.1 or 192.168.1.1 and I really could not come up with a good answer! Being an IT guy myself, I was obviously irritated by the fact that I hadn’t really thought about something that’s in my face all the time.

So why do most routers use this IP address? Well, it’s pretty simple actually. The reason is that the IP address is a non-routable IP address. A non-routable IP address, also known as a private IP address, is not assigned to any one organization and does not need to be assigned by an Internet Service Provider.

Some will argue that all IP addresses are routable, it’s just specific IP address ranges are not publicly routed on the Internet. Instead, they are routed through a NAT gateway or a proxy server before being connected to the Internet.

Private IP addresses are used in most large and small business networks because an ISP usually assigns only one public IP address to a location. IPv4 addresses have pretty much all run out and that’s why we have to rely on private IP addresses so much. When IPv6 arrives eventually, everyone will have a public IP address for every single device, but those days are still far off.

If there is more than one device that needs to connect to the Internet with only a single public IP, a NAT (Network Address Translation) gateway is used to translate all the private IP addresses to the public IP before going out to the Internet. Most of the time, the NAT device is also the router that gives out the private IP addresses to all the computers on the local network (DHCP server).

Officially, there are three private IP address ranges that have been defined by the IANA in RFC 1918:

IP address range

Number of Addresses

Class

10.0.0.0 – 10.255.255.255

16,777,216

Class A

172.16.0.0 – 172.31.255.25

1,048,576

Class B

192.168.0.0 – 192.168.255.255

65,536

Class C

 

Any private network in the world is using one of these three IP address ranges for their addressing scheme. The class is determined by the number of usable addresses in that range. Class A has well over 16 million usable addresses and is only needed by extremely large organizations that have hundreds of interconnected networks.

The reason why most routers come setup with a Class C IP address is because it can still handle over 65,000 IP addresses, enough for just about any home or small business.

The first usable address in the Class C network is 192.168.0.1, usually what the router is set to. However, I noticed in recent years that more brands are starting to use 192.168.1.1 as the default IP address, maybe because it’s easier to remember. Note that if you like, you could change the default IP address to either a Class B or Class A network IP and it would still work fine.

There is actually no other difference between the different private IP ranges besides the available number of addresses.

Note that there are other private IP address ranges, such as 1.0.0.0/8 and 2.0.0.0/8, but they are not being used. The other private IP addresses you may have seen are 169.254.x.x/16 and 127.x.x.x/8. These are called APIPA addresses and loopback addresses, respectively.

APIPA addresses are only used when there is no DHCP server to assign IP addresses. The devices will automatically assign an IP address to themselves in the range 169.254.0.0 to 169.254.255.255. This ensures that the devices can still communicate with other another even without a DHCP server or without having to manually assign IP addresses.

The loopback address is assigned to all network cards and is used for testing the card.

Anyway, so hopefully that explains a little bit about why routers have addresses like 192.168.0.1 or 10.0.1.1, etc. I’m sure my explanation was not perfect, so if I made any incorrect statement, please feel free to post a comment! Enjoy!