Routing - Routing Tables

Routing Basics

Introduction to Routing
- Routing is a straightforward concept used in networks to direct data.
- Routing tables are pivotal in determining how data is transmitted through networks.
History of Routers
- Early routers were basic computers equipped with two network interfaces.
- They bridged two networks and utilized manually updated routing tables.
- Modern operating systems maintain these routing tables to facilitate data transmission.
Building a Router
- One can still create a router using a computer with two network interfaces and a manual routing table.

Routing Table Components
- Routing tables can differ based on router types but share common elements:
- Destination Network
  - Contains a record for each network known to the router.
  - Includes network ID and netmask (could be in one or two columns).
  - Essential for identifying which IP addresses belong to which networks.
- Next Hop
  - Indicates the IP address of the next router for directed data.
  - Can specify if a network is directly connected.
- Total Hops
  - Indicates the distance (in hops) to the destination network.
  - Crucial for understanding routing efficiency on complex networks.
- Interface
  - Specifies which router interface will forward the traffic to the destination network.

Routing Dynamics
- Routers aim to choose the shortest route for effective data delivery.
- Network conditions can alter available paths, including:
- Routers going offline.
- Disconnected links.
- New routers being added.
- Traffic congestion affecting speed.
- Understanding how routers dynamically find the shortest path will be discussed further in future videos.
Routing Table Size
- Core Internet routers may contain millions of entries in their routing tables, each entry being consulted for every packet processed.
- This showcases the complexity and importance of routing tables in the functioning of modern networks.