Introduction to Dynamic Routing Protocol

1. Introduction to Dynamic Routing Protocol Routing Protocols and Concepts – Chapter 3

2. Objectives • Describe the role of dynamic routing protocols and place these protocols in the context of modern network design. • Identify several ways to classify routing protocols. • Describe how metrics are used by routing protocols and identify the metric types used by dynamic routing protocols. • Determine the administrative distance of a route and describe its importance in the routing process. • Identify the different elements of the routing table.

3. Context Index • 3.1 Introduction and Advantages • 3.2 Classifying Dynamic Routing Protocols • 3.3 Metrics • 3.4 Administrative Distance • 3.5 Routing Protocols and Subnetting Activities

4. 3.1 Introduction and Advantages

5. 3.1.1 Perspective and Background • The Evolution of Dynamic Routing Protocols.

6. 3.1.1 Perspective and Background • The Role of Dynamic Routing Protocol. • Function(s) of Dynamic Routing Protocols: • -Dynamically share information between routers. • -Automatically update routing table when topology changes. • -Determine best path to a destination.

7. 3.1.2 Network Discovery and Routing Table maintenance • The purpose of a dynamic routing protocol is to: • - Discover remote networks • - Maintaining up-to-date routing information • - Choosing the best path to destination networks • - Ability to find a new best path if the current path is no longer available

8. 3.1.2 Network Discovery and Routing Table maintenance What are the components of a routing protocol? • Data structures • Some routing protocols use tables and/or databases for its operations. This information is kept in RAM • Algorithm • In the case of a routing protocol algorithms are used for facilitating routing information and best path determination • Routing protocol messages • These are messages for discovering neighbors and exchange of routing information

9. 3.1.3 Advantages • Dynamic versus Static Routing

10. 3.2 Classifying Dynamic Routing Protocols

11. 3.2.1 Overview • Dynamic Routing Protocols Classification CCNP1中介绍

12. 3.2.2 IGP and EGP • Types of routing protocols: • -Interior Gateway Protocols (IGP) • -Exterior Gateway Protocols (EGP) • Interior Gateway Routing Protocols (IGP) • -Used for routing inside an autonomous system & used to route within the individual networks themselves. • -Examples: RIP, EIGRP, OSPF • Exterior Routing Protocols (EGP) • -Used for routing between autonomous systems • -Example: BGPv4

13. 3.2.2 IGP and EGP

14. 3.2.3 Distance Vector and Link State • Interior Gateway Protocols (IGPs) can be classified as two types: • Distance vector routing protocols • Link-state routing protocols • 距离矢量协议适用于以下情形： • 网络结构简单、扁平，不需要特殊的分层设计。 • 管理员没有足够的知识来配置链路状态协议和排查故障。 • 特定类型的网络拓扑结构，如集中星形(Hub-and-Spoke)网络。 • 无需关注网络最差情况下的收敛时间。

15. 3.2.3 Distance Vector and Link State • 链路状态协议适用于以下情形： • 网络进行了分层设计，大型网络通常如此。 • 管理员对于网络中采用的链路状态路由协议非常熟悉。 • 网络对收敛速度的要求极高。

16. 3.2.4 Classful and Classless Classful routing protocols do not send subnet mask information in routing updates. Classless routing protocols include the subnet mask with the network address in routing updates.

17. 3.2.5 Convergence • Convergence is defined as when all routers’ routing tables are at a state of consistency

18. 3.3 Metrics

19. 3.3.1 Purpose of a Metrics • Metric: • A metric is a value used by routing protocols to assign costs to reach remote networks.

20. 3.3.2 Metrics and Routing Protocols • Metrics used in IP routing protocols • - Bandwidth • - Cost • - Delay • - Hop count • - Load • - Reliability

21. 3.3.2 Metrics and Routing Protocols • The Metric Field in the Routing Table • Metric used for each routing protocol • -RIP - hop count • -IGRP & EIGRP - Bandwidth (used by default), Delay (used by default), Load, Reliability • -IS-IS & OSPF – Cost, Bandwidth (Cisco’s implementation)

22. 3.3.3 Load balancing • Load balancing • This is the ability of a router to distribute packets among multiple same cost paths.

23. 3.4 Administrative Distance

24. 3.4.1 Purpose of Administrative Distance • Purpose of a metric • It’s a calculated value used to determine the best path to a destination • Purpose of Administrative Distance • It’s a numeric value that specifies the preference of aparticular route

25. 3.4.1 Purpose of Administrative Distance • Identifying the Administrative Distance (AD) in a routing table • It is the first number in the brackets in the routing table

26. 3.4.1 Purpose of Administrative Distance

27. 3.4.2 Dynamic Routing Protocols

28. 3.4.2 Dynamic Routing Protocols • Show ip protocols可以看到该动态路由协议的管理距离。

29. 3.4.3Static Route3.4.4 Directly Connected Networks • Directly connected routes • Have a default AD of 0 • Static Routes • Have a default AD of 1

30. 路由比较— 哪条放到路由表中 • 192.168.1.0/24 [120/2] • 192.168.1.0/24 [110/200] • 192.168.1.0/24 [120/2] • 192.168.1.0/24 [120/5] • 192.168.1.0/24 [120/2] • 192.168.1.0/26 [100/50]

31. Summary • Dynamic routing protocols fulfill the following functions • -Dynamically share information between routers • -Automatically update routing table when topology changes • -Determine best path to a destination • Routing protocols are grouped as either • -Interior gateway protocols Or • -Exterior gateway protocols • Types of IGPs include • -Classless routing protocols - these protocols include subnet mask in routing updates • -Classful routing protocols - these protocols do not include subnet mask in routing update

32. Summary • Metrics are used by dynamic routing protocols to calculate the best path to a destination. • Administrative distance is an integer value that is used to indicate a router’s “trustworthiness” • Components of a routing table include: • -Route source • -Administrative distance • -Metric