693  Routing: Comprehensive Review

This chapter is a capstone for the routing material. It assumes you are already comfortable with the basic ideas from:

  • routing-fundamentals.qmd - what routers do, what routing tables look like.
  • routing.qmd - detailed examples, IoT-specific protocols like RPL, and energy trade-offs.

Use this review to test and deepen that understanding through scenario-based questions covering longest-prefix matching, loop prevention, and protocol trade-offs.

693.1 Learning Objectives

By the end of this review series, you will be able to:

  • Apply Longest Prefix Matching: Determine next-hop routers using routing table lookups
  • Compare Routing Protocols: Evaluate distance-vector vs link-state for different networks
  • Analyze Route Selection: Understand administrative distance and metric calculations
  • Debug Routing Issues: Diagnose routing loops, black holes, and suboptimal paths
  • Design Routing Tables: Plan efficient routing structures for IoT network deployments
  • Configure Redundant Paths: Implement floating static routes for automatic failover

693.2 Review Chapter Series

This comprehensive routing review is organized into three focused chapters:

693.2.1 1. Longest Prefix Matching

Master the fundamental algorithm routers use to select routes:

  • Route specificity: Why /24 routes beat /8 routes regardless of metrics
  • Common misconception: Lower metrics don’t always win - prefix length is king
  • Route summarization: Combining subnets to reduce table size
  • Practical examples: Step-by-step routing table lookups

Estimated time: 30 minutes

693.2.2 2. Convergence and Loop Prevention

Understand how routing protocols stabilize and prevent infinite loops:

  • Distance vector convergence: Calculate propagation time for multi-hop networks
  • TTL behavior: How Time-To-Live prevents packets from looping forever
  • Protocol trade-offs: Convergence speed vs battery life in IoT networks
  • Loop calculations: Determine exactly how many cycles before packet drop

Estimated time: 35 minutes

693.2.3 3. Advanced Configuration

Apply routing concepts to production IoT deployments:

  • Floating static routes: Configure automatic failover with metric-based priority
  • Router forwarding decisions: Trace step-by-step how routers select paths
  • Default routes: Essential for internet connectivity in IoT gateways
  • Cost analysis: Optimize backup path usage to minimize expenses

Estimated time: 35 minutes

693.3 Prerequisites

Required Chapters: - Routing Fundamentals - Core routing concepts - RPL Fundamentals - IoT routing protocol - Networking Fundamentals - Network basics

Routing Protocol Comparison:

Protocol Type Use Case IoT Relevance
RIP Distance Vector Small networks Legacy
OSPF Link-State Enterprise Edge routers
BGP Path Vector Internet Cloud connectivity
RPL Distance Vector IoT/WSN Primary IoT protocol

Total Estimated Time: 1.5 hours

Deep Dives: - Routing Fundamentals - Core routing concepts and algorithms - RPL Fundamentals - IoT routing protocol - RPL Production - Advanced RPL deployment

Comparisons: - Topologies - How topology affects routing - Networking Fundamentals - Network layer basics

Protocols: - Zigbee Architecture - AODV routing in Zigbee - Thread Fundamentals - RPL routing in Thread

Learning: - Quizzes Hub - Test your routing knowledge - Simulations Hub - Interactive routing tools

Enhance Your Learning:

  • Quizzes Hub - Test routing concepts with self-assessment quizzes covering longest prefix matching, TTL behavior, and protocol selection
  • Simulations Hub - Use interactive routing simulators to visualize convergence time, TTL decrementation, and loop detection
  • Videos Hub - Watch demonstrations of routing table lookups, RPL DODAG formation, and failover scenarios
  • Knowledge Gaps Hub - Address common routing misconceptions (e.g., “metrics always matter” vs “longest prefix wins first”)
  • Knowledge Map - See how routing connects to transport protocols, network topologies, and IoT mesh networks

Why These Hubs Matter: This comprehensive review consolidates routing knowledge, but the hubs provide hands-on practice and visual reinforcement. Use the Simulations Hub to experiment with routing table configurations without risk, and the Quizzes Hub to validate your understanding before exams or real-world deployments.

693.4 Key Concepts Overview

  • Longest Prefix Match: Routers select the most specific matching route (highest prefix length wins)
  • Convergence: Time for routing information to propagate through the network after changes
  • TTL (Time-To-Live): Safety mechanism preventing routing loops by limiting packet lifetime
  • Default Route: Catch-all route (0.0.0.0/0) for destinations without specific routes
  • Floating Static Routes: Backup routes with higher metrics that activate on primary failure
  • RPL Protocol: Distance-vector protocol optimized for low-power IoT mesh networks

693.5 Summary

This routing review series provides comprehensive coverage of routing concepts essential for IoT network design:

  1. Longest Prefix Matching - Route selection algorithm fundamentals
  2. Convergence and Loop Prevention - Protocol behavior and TTL safety
  3. Advanced Configuration - Production deployment patterns

Complete all three chapters to master routing for IoT deployments.

693.6 What’s Next

After completing this review series, continue to:

Wired Communication Protocols - RS-232 serial, I2C, SPI for device-to-device connections

Wireless Physical Layer Protocols - IEEE 802.15.4, Wi-Fi, Bluetooth operating characteristics

LPWAN Protocols - LoRaWAN, Sigfox, NB-IoT for long-range, low-power IoT

Start the review: Routing Review: Longest Prefix Matching