3.5 Compare and contrast static routing and dynamic routing

Static routing and dynamic routing differ in many regards, but the essence is the same. In order for a router to make a routing decision it needs routes entered into the routing table.
Static routes are fixed and do not allow for easy expansion or fault tolerance (although static routes can be programmed to offer fault tolerance).
Advantages of static routing:

  • Easy to implement in small networks
  • Low overhead (no routing protocol needs to run)
  • Secure (no routing messages exchanged)
  • Predictable

Disadvantages of static routing:

  • Not suitable for large networks other than the “Gateway of last resort” or “Default static route” routes
  • If a static route fails manual intervention is required to restore connectivity

Dynamic routing refers to the use of a routing protocol such as RIP/OSPF/EIGRP to automatically find routes and add them to the routing table. Dynamic routing also has the ability to “poison” or delete routes from the routing table and offer redundant routes in the event of a link failure.
Advantages of dynamic routing:

  • Suitable where two or more routers exist
  • Can grow with the size of the network
  • Reroutes traffic when conditions change

Disadvantages of dynamic routing:

  • Adds a processing overhead than can deteriorate routing performance in some circumstances
  • Increased security risks due to routing protocol messeges
  • Can only update routes based on topology and information it can gather
  • Adds network overhead

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