- Static vs. Dynamic Routing -

There are two basic methods of building a routing table:

> Static Routing

> Dynamic Routing

A static routing table is created, maintained, and updated by a network

administrator, manually. A static route to every network must be configured

on every router for full connectivity. This provides a granular level of

control over routing, but quickly becomes impractical on large networks.

Routers will not share static routes with each other, thus reducing

CPU/RAM overhead and saving bandwidth. However, static routing is not

fault-tolerant, as any change to the routing infrastructure (such as a link

going down, or a new network added) requires manual intervention. Routers operating in a purely static environment cannot seamlessly choose a better route if a link becomes unavailable. Static routes have an Administrative Distance (AD) of 1, and thus are always preferred over dynamic routes, unless the default AD is changed. A static route with an adjusted AD is called a floating static route.

Static Route Images:

 

A dynamic routing table is created, maintained, and updated by a routing

protocol running on the router. Examples of routing protocols include RIP

(Routing Information Protocol), EIGRP (Enhanced Interior Gateway

Routing Protocol), and OSPF (Open Shortest Path First).

Routers do share dynamic routing information with each other, which

increases CPU, RAM, and bandwidth usage. However, routing protocols are capable of dynamically choosing a different (or better) path when there is a change to the routing infrastructure.

Dynamic Routing Images:

 

Advantages and disadvantages of static routing:

Advantages of Static Routing

Ø Minimal CPU/Memory overhead

Ø No bandwidth overhead (updates are not shared

between routers)

Ø Granular control on how traffic is routed

Disadvantages of Static Routing

Ø Infrastructure changes must be manually adjusted

Ø No “dynamic” fault tolerance if a link goes down

Ø Impractical on large network

Advantages and disadvantages of dynamic routing:

Advantages of Dynamic Routing

Ø Simpler to configure on larger networks

Ø Will dynamically choose a different (or better)

route if a link goes down

Ø Ability to load balance between multiple links

Disadvantages of Dynamic Routing

Ø Updates are shared between routers, thus

consuming bandwidth

Ø Routing protocols put additional load on router

CPU/RAM

Ø The choice of the “best route” is in the hands of

the routing protocol, and not the network administrator