default routing, static routing and dynamic routing

Question

1. which routing type is best for a company that has one small branch office that is connected to an Internet Service Provider via one router and is not expected to grow or change in next three years.

 

2. Which routing types is best for a company that has a larger office building with three routers to interconnect within the building and also to connect to an Internet Service Provider. This larger office building is not expected to change in the next three years

 

3. Which routing types is best for a company that has a campus of buildings for its main headquarter and you have a rapidly changing and growing network at this headquarters as buildings are added, departments relocated, and routers are added

Answer 1

1) for a small branch office that is connected to an ISP, default routing makes things simple as we don’t expect the single router to learn the ISP routing table to make routing decisions. It keeps the FIB table of the router small and thereby not needing to upgrade the router over time.

2) Static routing works for the 3 router larger office building that connect to an ISP. Since the network would possibly grow after three years it expands the possibility of having an IGP to redistribute the static route and slowly migrate to having the network advertised via IGP

3) For Dynamic network scenarios, it’s best to use an IGP such as OSPF/ISIS to scale with the growth of the campus building routers. Its easier for the Admin to manage the network this way instead of configuring static routes every time the network grows which becomes a config management issue overtime.