What Is IP (Internet Protocol) Routing?

IP (Internet Protocol) Routing is a technology that allows a message to be delivered from one local network to another network over an IP network.

IP (Internet Protocol) Routing consists of the following components.

1. Host IP Configuration - Each host on an IP network must have one IP networking interface with the following minimum configuration as shown in this example:

Interface   : en0
IP Address  : 192.168.1.2
Subnet Mask : 255.255.255.0
Gateway     : 192.168.1.1

2. Gateway IP Routing - Each gateway connected to multiple subnets must have multiple networking interfaces. It must also perform the routing task with a routing table as shown in this example:

Subnet        Mask            Interface
192.168.0.0   255.255.255.0   fa0/0
192.168.1.0   255.255.255.0   fa0/1

3. IP Message Header - Each IP message must have a message header that contains the IP address of the message destination host as shown in the this diagram:

When a host on sends a message to another host on an IP network, the message will be delivered according the following algorithm:

1. If the source host has only one interface, the message will be delivered to that interface.

2. The interface will compare the destination address against the subnet mask of its configuration.

3. If the destination is in the same subnet, the message will be delivered to the destination directly.

4. If the destination is on a different subnet, the message will be delivered to the gateway of the interface configuration.

5. When the gateway receives the message, it will select one of subnet interfaces by comparing the destination address against its routing table and forward the message to the selected interface.

6. Repeat Step 2 to 5 until the messages reaches its destination.

⇒ Private IP vs. Public IP

⇐ What Is IP Gateway

⇑ IP Network

⇑⇑ Internet Connection - Frequently Asked Questions