 Welcome to IP Routing. In this learning activity, you'll explore how routers use routing tables to move data packets from their origin to their destination. In a network, routing is the path a data packet takes when it travels from the source to the destination. Along the way, it travels from router to router. Each one works independently to move the packet one step further along the route. No router knows the full path to the destination. They don't know where the packet was three steps before arriving or where it will be two steps after leaving. The router's job is to use its routing tables to move the packet one step closer to its destination. All network professionals need to understand routing because it's the foundation of how data travels on a network. Understanding how routers use routing tables helps you when something goes wrong. If a packet doesn't make it to its destination, you'll know where to start looking for the problem. Let's look at how this works. There are two types of devices on every network, end devices and routers. An end device doesn't know anything about routing other than its direct network connection and its gateway, which it uses to send packets out to other networks. Each router uses a routing table which lists the routes to other network destinations, including its direct connections. However, because each router works independently, they can't read each other's routing tables. Let's look at this in action. Our network is composed of routers and end devices. This device wants to send a packet to another computer. All it knows is the destination address is 5.4.3.5. How does it get the packet to where it's going? The originating device knows it has to send the packet to a different network because the network portion of the IP address is different from its own. So it sends the packet out to its gateway router, which uses its routing table to determine it has a direct connection to the destination. The router next door connects to the 5 network, so it sends the packet on to that router. The router next door uses the IP address to find the destination device. Let's look at a more complex example. This time, the sending device is on the 5 network and the destination address is 125.2.24.9. Just as before, the originating device sends the packet to its gateway router, which uses the routing table to find the next step needed to forward the packet to the 125 network. In this case, it's going to router D. Router D uses its table to determine the packet has to go to router B. Router B has the direct connection to the 125 network, so the packet moves to its final router before reaching the correct destination device. All routers use routing tables to forward a data packet from the sending device to the destination. Each router is unaware of the next router's tables. All each one can do is forward the packet to the next hop on the path. Today, you've examined how routing works. You've explored networks, routers, end devices, routing tables, and you've seen how they work together to move data packets along a path. Knowing how data travels helps you, as a data professional, when the network breaks down. You've completed IP routing.