16. Routers

Part 16 of Computer Networking Fundamentals: Routers

Routers

At the end of this episode, I will be able to:

1. Describe the basics of routers and the routing process.

Learner Objective: Describe the basics of routers and the routing process.

Description: In this episode, the learner will identify the basics of routing and the routing process.

• Introduction to Network Hardware
  • Routers+
    • Routers - a connectivity device that determines the short path to send traffic. Routers can send traffic to networks that they are not connected to. Routers use IP addresses to determine where to send traffic and operates on layer 3 of the OSI model.
    • Routing table - this routing element is a database that lists all the routes known to the router. These tables can be populated dynamically with a routing protocol or statically through manual configuration.
      • Components
        • Default route - is a route that routes traffic with no specific address of the next hop. In client computers this is typically the address of the default gateway.
        • Network Destination - the network IDs of known destination networks.
        • Netmask - the subnet mask for the destination network.
        • Gateway - the IP address of the next hop to which the packet will be forwarded.
        • Interface - this IP address or outgoing interface that connects to the destination network.
        • Metric - a value assigned call a cost assigned to reach the destination network. The lower the cost, the better the route.
    • Static vs. dynamic routing
      • Static routing - these are manually defined routes that are configured by and admin. These routes will not change if a shorter route is learned by dynamic routing protocols.
      • Dynamic routing - these are routes that are learning through routing protocols and communication with adjacent routers sharing routing information.
    • Routing protocols
      • Routing Information Protocol (RIP) - this is a dynamic routing protocol also known as a distance vector protocol that uses a hop count and the routing metric to determine the shortest path.
      • Open Shortest Path First (OSPF) - this is a dynamic routing protocol also known as a link state routing protocol. OSPF is a complex routing protocol that uses the topology information of the nearest neighbor routers to determine the shortest path.
      • Border Gateway Protocol (BGP) - this is a dynamic routing protocol used to determine the shortest path to route traffic across the Internet.
    • The routing process
      • When a router receives an IP packet, the router uses the destination IP address in the packet to determine where to send the packet. The router inspects it's routing table to identify the short path (route) to send the data.
    • Network Address Translation (NAT) - this is a routing technique that allows network devices within a LAN area network, using private IP addresses, to send traffic across the Internet by translating private and public IP addresses.