What is the Routing Information Protocol (RIP)?

If you’re just getting into networking, the idea of routers “talking” to each other might sound a little weird.  But believe it or not, that’s exactly what happens – and one of the oldest ways they do this is through something called RIP, short for Routing Information Protocol.

So, let’s break this down in a way that’s easy to follow.  Whether you’re a student preparing for CompTIA Network+, a curious techie, or someone diving headfirst into IT, this post will walk you through what RIP is, how it works, and why it’s still relevant (even if just barely) today.

What Are Interior Gateway Protocols (IGPs)?

Before we jump into RIP, let’s start with a quick pit stop:  What is an Interior Gateway Protocol?

Routers need a way to figure out the best path to send packets from one network to another.  That’s where routing protocols come in.  They let routers share information about network paths, kind of like how drivers use GPS or traffic apps to find the latest way home.

Now, there are two broad types of routing protocols:

• Interior Gateway Protocols (IGPs):  These are used for routing within a single autonomous system (AS).  An AS is just a fancy way of saying a network or group of networks under a single administrative domain (like a company or university).
• Exterior Gateway Protocols (EGPs):  These are used to route between autonomous systems.  The most famous example?  BGP (Border Gateway Protocol), which helps route traffic on the internet.

So RIP is an IGP.  It helps routers within the same organization or network share routing info and build routing tables.

Meet RIP:  The OG Routing Protocol

RIP is one of the oldest routing protocols around.  It’s been around since the early days of TCP/IP networks and was first standardized in RFC 1058 back in 1988.  That’s ancient in tech years. So what does RIP actually do? At its core, RIP:

• Shares information about which networks are reachable.
• Measures how far away those networks are using a simple metric:  hop count.
• Chooses the route with the least number of hops (i.e., routers) between point A & B.

Simple right?  Maybe a little too simple – but we’ll get to the downside later.

RIP Basics:  How It Works

Let’s walk through the basics of how RIP works in a real-world network.

• RIP-Enable Routers Talk to Each Other
  • Every 30 seconds, routers using RIP send out their entire routing tables to neighboring routers.  This is called a routing update.
  • Each entry in the table includes:
    • The destination network.
    • The number of hops to get there.
  • So imagine Router A says, “Hey Router B, I can get to Network 10.0.0.0 n 2 hops.”
  • Router B listens, updates its own table if that route is better than what it already has, and then passes that info along in the next update.
• Hop Count is Everything
  • RIP doesn’t care about bandwidth, delay, or reliability.  It only looks at how many routers (hops) a packet must pass through to reach its destination.
  • The maximum number of hops allowed in RIP is 15.  Anything more than that is considered unreachable.
  • So if Network X is 16 hops away, RIP won’t even try.
• RIP Uses Timers to Keep Everything Fresh
  • RIP is built on timers.  Here are the key ones:
    • Update Timer (30 seconds):  When routers send out routing updates.
    • Invalid Timer (180 seconds):  If a router doesn’t hear about a route in 180 seconds, it marks it as invalid.
    • Hold-Down Timer:  This helps stabilize the network by preventing routers from accepting potentially bad updates for a certain period.
    • Flush Timer (240 seconds):  This is how long a route will stay in the table before being removed.

Versions of RIP:  From RIPv1 to RIPv2

Like most tech, RIP has evolved over the years.  There are two main versions you should know about:

• RIPv1 (The Original)
  • RIPv1 is the OG version that came out in 1988.  It’s simple but has some big limitations:
    • Classful Routing Only:  It doesn’t send subnet mask info, so it assumes default masks (e.g., /8, /16, /24).
    • No Support for VLSM (Variable Length Subnet Masking):  This limits your ability to design flexible networks.
    • Broadcast Updates:  It uses broadcasts to share updates (255.255.255.255), which can be annoying on busy networks.
    • No Authentication:  Anyone can send routing updates.  That’s a big security hole.
• RIPv2 (The Upgrade)
  • RIPv2 was introduced in 1994 (RFC 2453), and it fixed a lot of the early problems:
    • Classless Routing:  Now it supports VLSM and subnet masks.
    • Multicast Updates:  It uses multicast (224.0.0.9) instead of broadcast, reducing unnecessary traffic.
    • Authentication Support:  You can require routers to authenticate routing updates (though it’s just basic password-based authentication).

If you’re using RIP today (not super common, but possible), you’re almost certainly using RIPv2.

Example:  RIP in Action

Let’s say you’ve got three routers:

• Router A (connected to 192.169.1.0/24)
• Router b (connected to 192.168.2.0/24)
• Router C (connected to 192.168.3.0/24)

All three routers are running RIPv2 and are directly connected in a triangle.

Each router:

1. Learns about its directly connected networks.
2. Sends its routing table to neighbors every 30 seconds.
3. Updates its table when it hears about new routes (with hop counts).

Eventually, all routers learn about all three networks, and each knows the best (shortest hop) path to reach each subnet.

Benefits of RIP

So why did people use RIP for so long?  And why do some still use it in labs or very small networks?

Here’s what RIP gets right:

• Easy to Configure
  • RIP is dead simple.  You can get it running in just a few lines of configuration.  It’s often used in teaching environments because it helps newbies understand routing without diving into complex metrics.
• Works in Small Networks
  • If your network has 5 – 10 routers & minimal change, RIP can still get the job done.  It’s lightweight and doesn’t need much memory or processing power.
• Supported Almost Everywhere
  • Because it’s old, RIP is supported on just about every router – even older devices.

Drawbacks of RIP

Now for the not-so-great stuff:

• Hop Count = A Poor Metric
  • RIP chooses routes based solely on hop count, not on quality.  So a 2-hop route over slow dial-up links might be chosen over a 3-hop route using fiber.  Not ideal.
• Scalability is Terrible
  • With a 15-hop limit, RIP just doesn’t scale.  Once your network gets large or complex, it starts to fall apart.
• Convergence is Slow
  • When there’s a network change (like a failed router), RIP can take minutes to converge – that’s the time it takes for all routers to agree on the new best paths.  Other protocols like OSPF & EIGRP do this in seconds.
• Vulnerable to Routing Loops
  • Without careful configuration, RIP can suffer from routing loops (where routers send packets in circles).  Techniques like split horizon, route poisoning, and hold-down timers help, but they’re more like Band-Aids than real fixes.

RIP Loop Prevention Mechanisms

Speaking of routing loops, let’s go over a few of RIP’s built-in defenses.

• Split Horizon
  • Don’t tell your neighbor about a route you learned from them.  It’s like saying, “Hey, I can get to that place through you” – which would create a loop.
• Route Poisoning
  • If a router detects that a route is down, it advertises it with a hop count of 16 (unreachable).  This tells everyone to stop using that route immediately.
• Hold-Down Timers
  • When a route is declared down, routers won’t accept new info about it for a set amount of time – even if someone claims it’s back.  This helps prevent bouncing & flapping routes.

Where is RIP Used Today?

So, is RIP still alive? Kind of.  It’s not used in large enterprise networks anymore – that job now belongs to OSPF, EIGRP, & BGP.  But RIP is still found in:

• Educational Environments:  RIP is easy to teach & visualize.
• Legacy Networks:  Some older devices or embedded systems still use RIP.
• Simple Test Labs:  It’s great for quick router simulations or packet tracer labs.

RIP vs. Other IGPs

Let’s stack RIP up against some of the big names in routing:

Should You Still Learn RIP?

Absolutely.  Even if you never use it in production, understanding RIP is foundational for learning how dynamic routing protocols work.  It sets the stage for understanding OSPF & EIGRP, which are more complex but use similar concepts.

Plus, if you’re studying for CompTIA Network+ Cisco CCNA, or other certs, you’ll definitely encounter RIP in the curriculum.

Quick RIP Configuration (Cisco Example)

If you’re using Cisco routers, here’s a quick & dirty RIP config to get you started:

• Router(config)# router rip
• Router(config-router)# version 2
• Router(config-router)# network 192.168.1.0
• Router(config-router)# network 192.168.2.0

Boom.  That’s it.  RIP is running.  Every 30 seconds, the router will send updates to its neighbors.

Key Takeaways

RIP may be outdated in many real-world environments, but there’s still a lot of value in learning how it works. Think of it as the “training wheels” of dynamic routing.  It teaches  you about routing tables, updates, metrics, convergence, and loop prevention – all crucial topics in networking.

So next time you see RIP mentioned in a lab or test question, don’t roll your eyes.  Give it a nod of respect – it helped build the internet we use today.