Why Use RIP Routing Protocol

Routing Information Protocol (RIP) is one of the oldest dynamic routing protocols still in use. It is a distance-vector protocol that uses hop count as its metric and sends periodic updates to neighbors. While modern networks often standardize on OSPF, EIGRP, or BGP, there are still valid scenarios where RIP is the simplest and most practical choice. In this article we look at what RIP does well, when it fits, and how to configure it on common platforms.

1. Core Characteristics of RIP

RIP operates using a very small and predictable feature set:

• Distance-vector protocol: Routers advertise entire routing tables to directly connected neighbors.
• Metric: Hop count, with a maximum of 15 hops. A hop count of 16 is considered unreachable.
• Periodic updates: Routing updates are sent every 30 seconds (RIPv1 and RIPv2 default).
• UDP based: Uses UDP port 520 to send and receive routing updates.
• Versions: RIPv1 (classful, no VLSM), RIPv2 (classless, supports VLSM and authentication), and RIPng for IPv6.

Because RIP has a very limited hop count and simple logic, it is inherently suited to small, stable topologies where complexity and optimization are not the primary concerns.

2. Why RIP Can Still Be the Right Choice

There are several reasons network engineers still use RIP in specific environments:

• Extremely simple configuration: RIP can be enabled with only a few lines of configuration, which is ideal for lab work, training, and very small branch networks.
• Legacy hardware and software: Some older routers, industrial devices, or embedded systems support only RIP as a dynamic routing protocol.
• Predictable behavior: Because the metric is hop based and the algorithm is simple, route selection is very easy to understand and troubleshoot.
• Low CPU and memory usage: RIP does not maintain a full link-state database and does not run computationally heavy SPF calculations.
• Isolated segments: For isolated test networks, air-gapped environments, or small labs, the limitations of RIP are often not a concern.

3. Basic RIP Configuration (Cisco IOS Style)

The following example shows a small three router lab where all routers participate in RIP version 2. The topology uses the 10.0.0.0/24 and 10.0.1.0/24 networks.

! On Router R1
router rip
 version 2
 no auto-summary
 network 10.0.0.0
 network 10.0.1.0

! On Router R2
router rip
 version 2
 no auto-summary
 network 10.0.0.0
 network 10.0.2.0

! On Router R3
router rip
 version 2
 no auto-summary
 network 10.0.1.0
 network 10.0.2.0

Key points in this configuration:

• version 2 ensures that classless RIPv2 is used rather than RIPv1.
• no auto-summary disables classful summarization at major network boundaries, which is important when using VLSM or discontiguous networks.
• The network statements enable RIP on interfaces whose IP addresses fall within the specified ranges.

4. Enabling RIPng for IPv6

RIPng extends RIP functionality to IPv6 networks. Configuration syntax is slightly different because IPv6 routing processes are created globally and then tied to interfaces.

ipv6 unicast-routing

ipv6 router rip LAB-RIPNG
 ! Optional timers can be tuned here

interface GigabitEthernet0/0
 ipv6 address 2001:db8:1::1/64
 ipv6 rip LAB-RIPNG enable

interface GigabitEthernet0/1
 ipv6 address 2001:db8:2::1/64
 ipv6 rip LAB-RIPNG enable

After enabling RIPng on interfaces, the routers will begin exchanging IPv6 routes using multicast address FF02::9.

5. Monitoring RIP Operation

Verification commands are simple and help confirm that RIP is converging as expected.

View the RIP routing table entries:

show ip route rip

Inspect the RIP process:

show ip rip database
show ip protocols

The show ip protocols command is especially useful. It reveals the update timer values, passive interfaces, and which networks are being advertised by the RIP process.

6. Limitations and Design Considerations

RIP is not an appropriate choice for every network. Understanding its limitations is critical:

• Maximum of 15 hops: Any destination 16 hops away or more is considered unreachable, which restricts RIP to small topologies.
• Slower convergence: Because RIP depends on periodic updates and incremental changes, it converges more slowly than modern link-state protocols.
• Single metric: Hop count does not consider bandwidth, delay, or reliability, which can result in suboptimal paths in more complex networks.
• Susceptible to routing loops: Split horizon, route poisoning, and hold-down timers reduce the risk but do not eliminate it entirely.
• Limited scalability: Large enterprise or service provider environments will quickly outgrow RIP.

RIP should generally be confined to very small deployments, such as lab topologies, legacy integrations, or simple hub-and-spoke networks where hop count remains low and the design is easy to visualize.

7. When RIP is a Good Fit

Despite its age, RIP can still be the correct protocol in the following situations:

• Training and certification labs where students need to grasp the basics of dynamic routing and observe metrics and updates in a simple way.
• Small branch offices with a few routers and predictable topology that require minimal effort to deploy and maintain.
• Legacy interoperability where older devices cannot support OSPF or other modern protocols but must still participate in dynamic routing.
• Test networks that are short lived and do not justify the operational overhead of a richer protocol.

Final Thoughts

RIP is no longer the primary choice for serious enterprise backbones, but it remains extremely useful as a teaching tool, a bridge to legacy equipment, and a quick way to enable dynamic routing in very small networks. Understanding RIP also provides foundational knowledge that makes it easier to learn more advanced protocols like OSPF and EIGRP. If your environment is small, simple, and stable, RIP can still deliver exactly what you need without unnecessary complexity.