Lecture CCNA Exploration 4.0 (Kỳ 2) - Chapter 4: Distance Vector Routing Protocols

The following will be discussed in this chapter: Identify the characteristics of distance vector routing protocols, describe the network discovery process of distance vector routing protocols using Routing Information Protocol (RIP), describe the processes to maintain accurate routing tables used by distance vector routing protocols,...
Nội dung trích xuất từ tài liệu:
Lecture CCNA Exploration 4.0 (Kỳ 2) - Chapter 4: Distance Vector Routing Protocols Chapter 4 – Distance Vector Routing Protocols CCNA Exploration version 4.0 Objectives • Identify the characteristics of distance vector routing protocols. • Describe the network discovery process of distance vector routing protocols using Routing Information Protocol (RIP). • Describe the processes to maintain accurate routing tables used by distance vector routing protocols. • Identify the conditions leading to a routing loop and explain the implications for router performance. • Recognize that distance vector routing protocols are in use today Học viện mạng Bách Khoa - Website: www.bkacad.com 2 Introduction to Distance Vector Routing Protocols Học viện mạng Bách Khoa - Website: www.bkacad.com 3 Distance Vector Routing Protocols 28 routers shown in the figure Học viện mạng Bách Khoa - Website: www.bkacad.com 4 Distance Vector Routing Protocols • Dynamic routing protocols help the network administrator overcome the time-consuming and exacting process of configuring and maintaining static routes. • What happens when a link goes down? • How do you ensure that redundant paths are available? Học viện mạng Bách Khoa - Website: www.bkacad.com 5 Distance Vector Routing Protocols Routing Information Protocol (RIP): RFC 1508 • Hop count is used as the metric • Maximum hop count is 15 • Routing updates are broadcast (ver1) or multicast (ver2) every 30 seconds Học viện mạng Bách Khoa - Website: www.bkacad.com 6 Distance Vector Routing Protocols Interior Gateway Routing Protocol (IGRP) • Proprietary protocol developed by Cisco. • Bandwidth, delay, load and reliability are used to create a composite metric. • Routing updates are broadcast every 90 seconds, • IGRP is the predecessor of EIGRP and is now obsolete Học viện mạng Bách Khoa - Website: www.bkacad.com 7 Distance Vector Routing Protocols Enhanced Interior Gateway Routing Protocol (EIGRP) • It can perform unequal cost load balancing. • It uses Diffusing Update Algorithm (DUAL) to calculate the shortest path. • Routing updates are sent only when there is a change in the topology. Học viện mạng Bách Khoa - Website: www.bkacad.com 8 Distance Vector Technology Học viện mạng Bách Khoa - Website: www.bkacad.com 9 Distance Vector Technology • The Meaning of Distance Vector: a router using distance vector routing protocols knows 2 things: 1. Distance to final destination 2. Vector or direction traffic should be directed • Routers using distance vector routing are not aware of the network topology. • The router knows only: 1. The direction or interface in which packets should be forwarded 2. The distance or how far it is to the destination network Học viện mạng Bách Khoa - Website: www.bkacad.com 10 Characteristics of DV Routing Protocol 1.Periodic updates 2.Neighbors: Routing by rumor 3.Broadcast updates 255.255.255.255 4.Entire routing table is included with routing update Học viện mạng Bách Khoa - Website: www.bkacad.com 11 Routing by Rumo (hop-by-hop update) Học viện mạng Bách Khoa - Website: www.bkacad.com 12 Characteristics of DV Routing Protocol Animation 4.1.2.2 Học viện mạng Bách Khoa - Website: www.bkacad.com 13 Routing Protocol Algorithms • The algorithm used for the routing protocols defines the following processes: 1. Mechanism for sending and receiving routing information. 2. Mechanism for calculating the best paths and installing routes in the routing table. 3. Mechanism for detecting and reacting to topology changes. Animation 4.1.3 Học viện mạng Bách Khoa - Website: www.bkacad.com 14 Routing Protocol Characteristics • Criteria used to compare routing protocols includes: 1. Time to convergence 2. Scalability 3. Classless (use of VLSM) or Classful 4. Resource usage 5. Implementation & maintenance Học viện mạng Bách Khoa - Website: www.bkacad.com 15 Routing Protocol Characteristics Học viện mạng Bách Khoa - Website: www.bkacad.com 16 Distance Vector Routing Protocols Animation 4.1.4.2 Học viện mạng Bách Khoa - Website: www.bkacad.com 17 Network Discovery Học viện mạng Bách Khoa - Website: www.bkacad.com 18 Cold Start Router initial start up
After a cold start and before the exchange of routing information, the routers initially discover their own directly connected networks and subnet masks. Animation 4.2.1.1 Học viện mạng Bách Khoa - Website: www.bkacad.com 19 Exchange of Routing Information Initial Exchange: Animation 4.2.2 • If a routing protocol is configured then – Routers will exchange routing information • Routing updates received from other routers.Router checks update for new information. If there is new information: 1. Metric is updated 2. New information is stored in routing table • Router convergence is reached when all routing tables in the network contain the same network information Routers continue to exchange routing information. • If no new information is found then Convergence is reached Học viện mạng Bách Khoa - Website: www.bkacad.com 20 ...