There is a range for each of the three classes of IP addresses used for networking:

    * Range 1: Class A - 10.0.0.0 through 10.255.255.255
    * Range 2: Class B - 172.16.0.0 through 172.31.255.255
    * Range 3: Class C - 192.168.0.0 through 192.168.255.255

Although each range is in a different class, your are not required to use any particular range for your internal network. It is a good practice, though, because it greatly diminishes the chance of an IP address conflict.
 
Multi-homing

 

As businesses rely more and more on the Internet, having multiple points of connection to the Internet is fast becoming an integral part of their network strategy. Multiple connections, known as multi-homing, reduces the chance of a potentially catastrophic shutdown if one of the connections should fail.

 

In addition to maintaining a reliable connection, multi-homing allows a company to perform load-balancing by lowering the number of computers connecting to the Internet through any single connection. Distributing the load through multiple connections optimizes the performance and can significantly decrease wait times.

 

Multi-homed networks are often connected to several different ISPs (Internet Service Providers). Each ISP assigns an IP address (or range of IP addresses) to the company. Routers use BGP (Border Gateway Protocol), a part of the TCP/IP protocol suite, to route between networks using different protocols. In a multi-homed network, the router utilizes IBGP (Internal Border Gateway Protocol) on the stub domain side, and EBGP (External Border Gateway Protocol) to communicate with other routers.