ROLO

192.168.1.1 is an IP address that is within the private IP address range: 192.168.0.0 - 192.168.255.255

These IP addresses are special, because they can be used many times over on different networks. In other words, two people can have 192.168.0.0/16 networks at the same time.

The downside is that private IP address ranges are considered non-routable. What does that mean? that private IP addresses cannot communicate on the Internet without the use of Network Address Translation (NAT).

There are three private IP address ranges defined by RFC 1918:

• 10.0.0.0 - 10.255.255.255
• 172.16.0.0 - 172.31.255.255
• 192.168.0.0 - 192.168.255.255

When 192.168.1.1 is used as a Default IP Address

Some network devices, use 192.168.1.1 as their default IP address. For example: LinkSys routers.

Since two devices on a network cannot share one IP address, this can create difficulties. One person can have one device on the network at the IP address 192.168.1.1 and another person can have a different device on another network at the IP address 192.168.1.1, but neither of them can have two devices on the same network if both use the 192.168.1.1 IP address.

So, when you add a new device to your network, make sure that its default IP address is not already in use.

The Internet RFC’s define 192.168.1.1

RFC 1918 officially defines 192.168.1.1 in: RFC 1918: Address Allocation for Private Internets:

The Internet Assigned Numbers Authority (IANA) has reserved the following three blocks of the IP address space for private internets:

• 10.0.0.0 - 10.255.255.255 (10/8 prefix)
• 172.16.0.0 - 172.31.255.255 (172.16/12 prefix)
• 192.168.0.0 - 192.168.255.255 (192.168/16 prefix)

Other Private IP Addresses in Common Use

• 192.168.0.1
• 192.168.2.1

Whats the joke?

A frequent joke on the internet is convincing newbies to connect to 127.0.0.1, but what is this address really?

127.0.0.1 is the standard IP address used for a loopback network connection.

This means that when you try to connect to 127.0.0.1, you are looped back to your own machine.

If you connect using telnet, ftp, etc… to 127.0.0.1, you will be connected to your own machine.

So, simply put, 127.0.0.1 is you.

127.0.0.1 is also called localhost.

Actually, any IP address in the 127.x.x.x range functions in the same manner. 127.0.0.1 is just the one that is more commonly used.

The Internet RFC’s definition of 127.0.0.1

The proper use of 127.0.0.1 is defined in RFC 3330: Special-Use IPv4 Addresses:

127.0.0.0/8 - This block is assigned for use as the Internet host loopback address. A datagram sent by a higher level protocol to an address anywhere within this block should loop back inside the host. This is ordinarily implemented using only 127.0.0.1/32 for loopback, but no addresses within this block should ever appear on any network anywhere.

The IPv6 version of localhost is defined in RFC 3513: Internet Protocol Version 6 (IPv6) Addressing Architecture as ::1/128.