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Distance Vector Routing Protocol (RIP)

Definition

A Distance Vector Routing Protocol is a routing method where routers share information about:

  • Distance (metric)
  • Direction (next hop)

RIP (Routing Information Protocol) is a simple distance vector protocol that uses hop count to determine the best path.

Key Points

  • RIP = Routing Information Protocol
  • Type: Distance Vector
  • Metric: Hop Count
  • Maximum hops: 15 → Hop 16 = unreachable
  • Administrative Distance (AD): 120
  • Updates sent every 30 seconds
  • Works best in small networks
  • Supports equal-cost load balancing (up to 4 by default, 6 maximum)

💡 Load Balancing: Traffic is distributed equally across multiple equal-cost paths.

Example / Code

Router(config)# router rip
Router(config-router)# network 192.168.1.0
Router(config-router)# network 192.168.2.0
Router(config-router)# network 192.168.3.0
Router(config-router)# network 192.168.4.0

Router(config-router)# passive-interface serial 2/0
Router(config-router)# do show ip route

Explanation

  • router rip → Enables RIP routing
  • network → Advertises connected networks
  • passive-interface → Stops sending updates on that interface
  • show ip route → Displays routing table

Output (if any)

Example routing table entry:

R 192.168.2.0/24 [120/1] via 192.168.1.1
  • R → Learned via RIP
  • 120 → Administrative Distance
  • 1 → Hop count

Common Mistakes

  • ❌ Using RIP in large networks (not scalable)
  • ❌ Forgetting hop limit (15 max)
  • ❌ Misunderstanding load balancing (only equal-cost paths)
  • ❌ Not enabling correct networks
  • ❌ Confusing classful vs classless behavior

Short Exam Notes (very concise revision points)

  • RIP = Distance Vector
  • Metric = Hop count
  • Max hops = 15
  • AD = 120
  • Updates every 30s
  • Small networks only

RIP Versions

Definition

RIP has multiple versions with different capabilities for IPv4 and IPv6.

Key Points

  • RIPv1

    • Classful (no subnet mask info)
    • No VLSM support
    • Broadcast updates

  • RIPv2

    • Classless (supports subnet masks)
    • Supports VLSM
    • Uses multicast (224.0.0.9)
    • Supports authentication (MD5 / plaintext)

  • RIPng

    • Used for IPv6

Example / Code

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

Explanation

  • version 2 enables RIPv2
  • RIPv2 improves efficiency using multicast instead of broadcast
  • Supports modern subnetting (VLSM)

Output (if any)

Routing table still shows:

R 192.168.1.0/24 [120/1] via 192.168.1.1

Common Mistakes

  • ❌ Using RIPv1 with VLSM networks
  • ❌ Forgetting to enable version 2
  • ❌ Confusing multicast vs broadcast

Short Exam Notes (very concise revision points)

  • RIPv1 = Classful
  • RIPv2 = Classless + VLSM
  • RIPng = IPv6
  • Multicast: 224.0.0.9

RIP Message Types

Definition

RIP uses specific messages to exchange routing information between routers.

Key Points

  • Request Message

    • Sent when router starts
    • Asks neighbors for routing table

  • Response Message

    • Contains routing table
    • Sent as reply or periodic update

Example / Code

(No direct CLI command — happens automatically when RIP is enabled)

Explanation

  • When a router starts → sends Request
  • Neighbor routers reply with Response
  • Periodically, routers send responses every 30 seconds

Output (if any)

(Not directly visible, but affects routing table updates)

Common Mistakes

  • ❌ Thinking messages must be configured manually
  • ❌ Not understanding startup behavior

Short Exam Notes (very concise revision points)

  • Request → ask for routes
  • Response → send routes
  • Auto process

Difference Between RIP and IGRP

Definition

RIP and IGRP (Interior Gateway Routing Protocol) are both distance vector protocols but differ in performance and scalability.

Key Points

FeatureRIPIGRP
Network SizeSmallLarge
MetricHop countBandwidth + delay
Max Hops15255
AD120100
Update Time30 sec90 sec
AS NumberNot usedRequired

Example / Code

RIP: router rip
IGRP: router igrp 1

Explanation

  • RIP is simple but limited
  • IGRP is more advanced (uses composite metric)
  • Lower AD (100) means IGRP is preferred over RIP

Output (if any)

Example:

I 192.168.1.0/24 [100/10] via 192.168.1.1
R 192.168.2.0/24 [120/1] via 192.168.1.2

Common Mistakes

  • ❌ Thinking RIP is better for large networks
  • ❌ Ignoring AD when comparing protocols
  • ❌ Forgetting IGRP uses multiple metrics

Short Exam Notes (very concise revision points)

  • RIP → simple, small networks
  • IGRP → advanced, larger networks
  • RIP AD = 120, IGRP AD = 100
  • RIP = hop count, IGRP = bandwidth + delay