Routing protocols use different criteria to determine the best path to a destination.
As an example with static routes the administrator
decides which path the traffic will take.
With RIP, hop count is the determining factor or criteria
and with OSPF, bandwidth is the determining factor.
We as humans do this all the time when driving from point A to point B
we will determine the best path to take based on criteria,
such as the speed limit, congestion on a highway
or motorway, the amount of time we have
and perhaps some other criteria. Essentially you are working out
the best route to take from point A to point B
based on some criteria that’s important to you,
typically to get from point A to point B in the shortest time possible.
In the same way in this topology,
when traffic is sent from San Francisco to San Jose
which path will the traffic take?
As an example, when using the RIP routing protocol,
RIP would send the traffic directly from San Francisco to San Jose.
RIP doesn’t take bandwidth into account,
so if we had a network of 10.1.1.0 in San Francisco
and a network of 10.1.2.0 in San Jose
RIP would take the direct path between those 2 networks
and that’s because the number of hops is less than going via New York.
RIP will not send traffic via New York
it would send the traffic directly between San Francisco and San Jose.
RIP, however, is not considering the bandwidth of the links
so even though there are fewer hops
it may be quicker to send the traffic via New York rather than directly.
OSPF, on the other hand, takes bandwidth into account.
So, in this case, OSPF would send the traffic via New York
because the link speeds are greater.
OSPF is a more powerful routing protocol and makes better decisions
because it takes bandwidth into account when determining the best path.
RIP doesn’t, it simply looks at the number of hops from point A to point B.
This is a very basic topology
simply used as an example to show you how routing protocols
determine the best path or best route to a destination.
The moral of the story is as follows:
different routing protocols have different criteria
to determine the best path from A to B.
OSPF once again takes bandwidth into account when determining the best path.
RIP doesn’t, some routing protocols will make better decisions than other routing protocols.
Generally, today you’re going to use either OSPF or EIGRP in most enterprise networks.
EIGRP is a popular routing protocol when you have a Cisco-only network.
EIGRP is a proprietary Cisco routing protocol
and may not be supported by other vendors
OSPF is an industry standard routing protocol
and is therefore better to use when you have a multi-vendor network.