The Wonderful World of Routing

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The Wonderful World of Routing

In this section, we will explore the wonderful world of routing. This means exploring how internet routers function, understanding and describing the different dynamic routing technologies, and learning how to successfully install and configure a router.

How does an internet router work? Most people’s first exposure to routers is their home router. This connects your personal PC to your Internet Service Provider, or ISP. The router sends and receive packets to the proper destination by referring to a routing table to determine the correct IP address to send to. These home routers typically have two ports for the row and column of the routing table. The next three ports handle the gateway, or next IP, and the interface, or which port to use. In summary, the router compares the IP address to its routing table and then decides based on this information.

NAT, or Network Address Translation, is a dynamic routing technology that is built to address TCP/IP issues. This technology allows routers to hide a computer’s IP address from outside networks, enables computers on LAN to communicate with outside networks, and conserves your IP address. Before this tech, IP addresses had to be assigned to each computer and all LAN hosts had access to the gateway router’s IP address. An overloaded NAT may be referred to as PAT, or Port Address Translation.

RIPv1 is a distance vector routing protocol, this means it can calculate the efficiency of your network’s routes. This technology required frequent updating which led to slowdowns, and it was eventually replaced by RIPv2 in 1994 which is the current version of RIP. BGP is another technology that re-organized the internet into a multi-tiered autonomous system. OSPF, or Open Shortest Path First, is the most commonly used interior gateway protocol across the internet. IS-IS is another method that only sends updates to routing tables, a technology that has worked with IPv6 from the beginning. Lastly, EIGRP or Enhanced Interior Gateway Routing Protocol is a hybrid tech that uses both distance vector and link state protocols. This proprietary technology is losing market share to open source alternatives like OSPF.

How do you install a router in the first place? Surprisingly enough, the physical installation of a router is relatively straightforward. First, connect the power cable to your router. For a business class router, insert it into the rack and connect the power cable. After connecting power, plug in your connections. To configure the router, you will need a Yost cable or rollover cable. This cable is connected to the console port and a terminal emulation program like PuTTY or HyperTerminal. Afterward, the serial port settings should be set to 9600 baud, 8 data bits, 1 stop bit, and no parity. Configuring these routers may require sophisticated training, but newer routers offer some guidance in the process. Many business-class routers these days employ a web-based access system that allows you to configure the router online. These connections can be managed with Network Management Software or NMS.

At the most basic level, a router must have at least two connections, be properly configured on every port, and ensure the routing table is sending packets where they need to go. Some routers may be equipped with a USB port or alternate ways to connect. First, you want to set up the WAN side of the network where the router connects to the ISP. Next, you want to set up the LAN where computers connect to the network. Finally, you want to establish routes to the network. This is typically done by the router when building a routing table, but may require the IOS command line on Cisco routers. An optional fourth step would be to configure a dynamic protocol. This is typically unnecessary unless you are dealing with two or more routers. If you are having issues with your router, you can use programs like traceroute to find issues with your connection.

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