In computer networks, what is the Routing Information Protocol (RIP) and how does it share routing information between routers?

Introduction / Context:
Routing Information Protocol, usually abbreviated as RIP, is one of the earliest dynamic routing protocols used in Internet Protocol networks. It helps routers automatically share information about reachable networks so that data packets can be forwarded along appropriate paths. Although newer protocols have replaced RIP in many modern networks, it is still important for interview questions and basic networking courses because it illustrates distance vector concepts and simple metrics like hop count.

Given Data / Assumptions:

• We are working in an IP based routed network with multiple routers.
• RIP is a dynamic routing protocol that runs between routers.
• RIP is classified as a distance vector protocol.
• Hop count is used as the primary routing metric.

Concept / Approach:
RIP operates by having each router periodically send its entire routing table to its neighbours. Each route includes a destination network and a hop count, which is the number of routers a packet must pass through to reach that network. When a router receives updates from neighbours, it adds one to the hop count and compares routes, selecting paths with the lowest hop count. RIP has a maximum hop count of 15, which limits the size of networks it can support but also prevents routing loops from persisting indefinitely. Because RIP is distance vector, routers know only the direction and distance to a destination, not the full path.

Step-by-Step Solution:
Step 1: Recognise that RIP is used between routers, not end user devices, to exchange information about reachable networks.Step 2: Understand that RIP routers maintain routing tables listing destination networks and associated hop counts.Step 3: Note that at regular intervals, typically every thirty seconds, each RIP router broadcasts or multicasts its routing table to its neighbours.Step 4: When a router receives an update, it increments the hop count for each route and compares it with existing entries, keeping the route with the lowest hop count.Step 5: Realise that if the hop count for a route reaches sixteen, RIP treats the network as unreachable, which helps control routing loops.

Verification / Alternative check:
You can verify that RIP is distance vector by examining routing tables and update messages on a lab router. The router does not store the entire path, only a next hop and a hop count. Packet captures of RIP updates show periodic messages containing network prefixes and hop counts. The absence of link state information or full topology data confirms that RIP is not a link state protocol. Also, the presence of a hop count limit demonstrates one of the main design characteristics of RIP.

Why Other Options Are Wrong:
Option B describes a link state routing protocol that uses Dijkstra shortest path algorithm, which fits protocols like OSPF, not RIP. Option C refers to an application layer file transfer protocol, which is more like FTP, not a routing protocol. Option D mentions a wireless encryption standard, which is unrelated to routing and belongs to security mechanisms such as WPA or WPA2. These options do not correctly describe RIP or its behaviour.

Common Pitfalls:
A common mistake is to assume that RIP is suitable for very large or complex networks. Because it uses hop count and has a maximum of fifteen hops, it is best suited for small to medium networks. Another pitfall is ignoring convergence time. RIP can take longer to converge after topology changes compared to more advanced protocols like OSPF or EIGRP. Network designers should understand these limitations and use RIP only in environments where its simplicity is an advantage and where network size and performance requirements are modest.

Final Answer:
Correct answer: A distance vector routing protocol that uses hop count as a metric to share routes periodically between routers