Lecture CCNA Exploration 4.0 (Kỳ 2) - Chapter 10: Link-State Routing Protocols

Upon completion of this lesson, the successful participant will be able to: Describe the basic features & concepts of link-state routing protocols, list the benefits and requirements of link-state routing protocols.
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Lecture CCNA Exploration 4.0 (Kỳ 2) - Chapter 10: Link-State Routing Protocols Chapter 10: Link-State Routing Protocols CCNA Exploration version 4.0 Objectives • Describe the basic features & concepts of link-state routing protocols. • List the benefits and requirements of link-state routing protocols. Học viện mạng Bach Khoa - Website: www.bkacad.com 2 Link-State Routing Học viện mạng Bach Khoa - Website: www.bkacad.com 3 Link-State Routing Protocols • Link state routing protocols – Also known as shortest path first algorithms – Built around Dijkstra’s SPF Học viện mạng Bach Khoa - Website: www.bkacad.com 4 Introduction to the SPF Algorithm • Dikjstra’s algorithm also known as the shortest path first (SPF) algorithm. This algorithm accumulates costs along each path, from source to destination. • Each router determines its own cost to each destination in the topology. Học viện mạng Bach Khoa - Website: www.bkacad.com 5 Introduction to the SPF Algorithm Học viện mạng Bach Khoa - Website: www.bkacad.com 6 Introduction to the SPF Algorithm • The shortest path to a destination is not necessarily the path with the least number of hops Học viện mạng Bach Khoa - Website: www.bkacad.com 7 Link-State Routing Process • How routers using Link State Routing Protocols reach convergence 1. Each routers learns about its own directly connected networks. 2. Link state routers exchange hello packet to “meet” other directly connected link state routers. 3. Each router builds its own Link State Packet (LSP) which includes information about neighbors such as neighbor ID, link type, & bandwidth. 4. After the LSP is created the router floods it to all neighbors who then store the information and then forward it until all routers have the same information. 5. Once all the routers have received all the LSPs, the routers then construct a topological map of the network which is used to determine the best routes to a destination. Học viện mạng Bach Khoa - Website: www.bkacad.com 8 1.Learning about Directly Connected Network • Link: this is an interface on a router • Information about the state of those links is known as link- states.This information includes: – The interface's IP address and subnet mask. – The type of network, such as Ethernet (broadcast) or Serial point-to-point link. – The cost of that link. – Any neighbor routers on that link. Học viện mạng Bach Khoa - Website: www.bkacad.com 9 2.Sending Hello Packets to Neighbors • Routers with link-state routing protocols use a Hello protocol to discover any neighbors on its links. A neighbor is any other router that is enabled with the same link-state routing protocol. Học viện mạng Bach Khoa - Website: www.bkacad.com 10 2.Sending Hello Packets to Neighbors Học viện mạng Bach Khoa - Website: www.bkacad.com 11 2.Sending Hello Packets to Neighbors • When 2 link-state routers learn that they are neighbors, they form an adjacency. • These small Hello packets continue to be exchanged between two adjacent neighbors which serve as a keepalive function to monitor the state of the neighbor. • If a router stops receiving Hello packets from a neighbor, that neighbor is considered unreachable and the adjacency is broken. Học viện mạng Bach Khoa - Website: www.bkacad.com 12 3.Building the Link-State Packet • Each router builds its own Link State Packet (LSP). • Contents of LSP: 1. State of each directly connected link 2. Includes information about neighbors such as neighbor ID, link type, & bandwidth. Học viện mạng Bach Khoa - Website: www.bkacad.com 13 3.Building the Link-State Packet Học viện mạng Bach Khoa - Website: www.bkacad.com 14 4.Flooding Link-State Packets to Neighbors • Each router floods the LSP to all neighbors, who then store all LSPs received in a database. • Each router floods its link-state information to all other link-state routers in the routing area. • Whenever a router receives an LSP from a neighboring router, it immediately sends that LSP out all other interfaces except the interface that received the LSP. Học viện mạng Bach Khoa - Website: www.bkacad.com 15 4.Flooding Link-State Packets to Neighbors • LSPs are sent out under the following conditions 1. During initial startup of the router or of the routing protocol process on that router 2. Whenever there is a change in the topology, including a link going down or coming up, or a neighbor adjacency being established or broken Học viện mạng Bach Khoa - Website: www.bkacad.com 16 4.Flooding Link-State Packets to Neighbors Học viện mạng Bach Khoa - Website: www.bkacad.com 17 4.Flo ...