Dynamic Routing Protocols Overview

Dynamic Routing Overview

• Dynamic routing protocols automatically discover and maintain routing information, updating as the network changes.
• Network changes are handled by finding new paths and adjusting the routing tables in real-time.
• Key features include discovering remote networks, maintaining current routing tables, determining optimal paths, and adjusting to network changes swiftly.

Advantages and Disadvantages

• Advantages: Reduced administrative overhead, automatic topology adaptability, well-suited for complex networks.
• Disadvantages: Router resource consumption (CPU and bandwidth), slower convergence than static routing, increased troubleshooting complexity.

Dynamic Routing Protocol Types

• Distance-Vector Protocols:
  • Exchange routing updates with neighbouring routers (e.g., RIP, EIGRP).
  • Utilize metrics like hops, cost, or delay to determine path quality.
  • Do not maintain a complete network topology map.
• Link-State Protocols:
  • Create a complete network topology map (e.g., OSPF, IS-IS).
  • Employ algorithms (like Dijkstra's) to find shortest paths.
• Hybrid Protocols:
  • Combine elements of both types (e.g., EIGRP).

Routing Protocol Classifications

• Classful vs. Classless:
  • Classful protocols (like RIPv1, IGRP) lack subnet mask information.
  • Classless protocols (like RIPv2, EIGRP, OSPF) support Variable Length Subnet Masking (VLSM) and Classless Inter-Domain Routing (CIDR).
• Interior Gateway Protocols (IGP):
  • Used within an Autonomous System (e.g., RIP, EIGRP, OSPF).
• Exterior Gateway Protocols (EGP):
  • Used between Autonomous Systems (e.g., BGP).

Key Routing Metrics

• Hops: Number of routers to reach a destination.
• Bandwidth: Network link capacity.
• Delay: Time to traverse a connection.
• Reliability: Link stability.
• Load: Network usage.

Distance-Vector Protocols Details

• RIP:
  • Updates every 30 seconds.
  • Maximum hop count: 15.
  • Uses the Bellman-Ford algorithm.
• EIGRP:
  • Employs the DUAL algorithm for fast convergence.
  • Supports multiple network layer protocols.
  • Updates sent only when the topology changes.

Link-State Protocols Details

• OSPF:
  • Creates a topology map through Link-State Advertisements (LSAs).
  • Faster convergence, using Dijkstra's algorithm.
• IS-IS:
  • Commonly used in provider networks.
  • Similar functionality to OSPF.

Routing Table Concepts

• Route Types:
  • Directly connected, static, or dynamically learned routes.
• Lookup Process:
  • Finds the longest prefix match for a destination IP address.
  • Prioritizes routes with lower administrative distances.

Administrative Distance

• Measures routing source reliability.
• Directly connected: 0 (most preferred).
• Static routes: 1.
• RIP: 120, OSPF: 110, EIGRP: 90.

Convergence

• Network convergence means all routers have consistent, accurate routing information.
• Distance-vector protocols (like RIP) are typically slower to converge.
• Link-state protocols (like OSPF) converge more quickly.

Study Focus

• Understand the features and differences between RIP, EIGRP, and OSPF.
• Master how routes are selected based on metrics and administrative distance.
• Practice interpreting routing tables and tracing packet paths.