Link state routing protocols however also have drawbacks or disadvantages
the first disadvantage is that they have a greater demand for resources
than distance vector routing protocols do.
Link state routing protocols require more memory
the routers have multiple tables
so for example, they’ll have a peer table or neighbor table
they’ll have a topology table or Link State Database also called LSDB database
and they have a routing table.
More memory is required to hold multiple tables
then would be necessary with a distance vector routing protocol.
There’s also more demand on the CPU of the router or switch when running OSPF or ISIS.
The Dijkstra algorithm can be very process intensive
especially when there are a lot of changes in the topology.
Link state routing protocols also requires strict designs
in OSPF as an example, area 0 is always required when you have more than 1 area.
All other area have to touch the backbone area or area 0.
All traffic from 1 area to another area has to traverse the backbone area.
The configuration of OSPF is, therefore, more complex
than distance vector routing protocol such as RIP.
However, the advantages of link state routing protocols generally far out way
the disadvantages and this is especially true in large environments.
Thus in large topologies, OSPF is seen as a much better choice than RIP.