Both de facto and proprietary interior protocols are in use today. Which of the following is a proprietary interior protocol that chooses the best path between the source and destination?

A.
IGRP

B.
RIP

C.
BGP

D.
OSPF

Explanation:
A: Interior Gateway Routing Protocol (IGRP) is a distance-vector routing protocol that was developed by, and is proprietary to, Cisco Systems. Whereas Routing Information
Protocol (RIP) uses one criterion to find the best path between the source and the destination, IGRP uses five criteria to make a “best route” decision. A network administrator
can set weights on these different metrics so that the protocol works best in that specific environment.
B is incorrect because Routing Information Protocol (RIP) is not proprietary. RIP is a standard that outlines how routers exchange routing table data and is considered a
distance-vector protocol, which means it calculates the shortest distance between the source and the destination. It is considered a legacy protocol, because of its slow
performance and lack of functionality. It should only be used in small networks. RIP version 1 has no authentication, and RIP version 2 sends passwords in clear text or hashed
with MD5.
C is incorrect because the Border Gateway Protocol (BGP) is an Exterior Gateway Protocol (EGP). BGP enables routers on different ASs to share routing information to
ensure effective and efficient routing between the different networks. BGP is commonly used by Internet service providers to route data from one location to the next on the
Internet.
D is incorrect because Open Shortest Path First (OSPF) is not proprietary. OSPF uses link-state algorithms to send out routing table information. The use of these algorithms
allows for smaller, more frequent routing table updates to take place. This provides a more stable network than RIP but requires more memory and CPU resources to support
this extra processing. OSPF allows for a hierarchical routing network that has a backbone link connecting all subnets together. OSPF is the preferred protocol and has replaced
RIP in many networks today. Authentication can take place with clear text passwords or hashed passwords, or you can choose to configure no authentication on the routers
using this protocol.