Week 10-11 Routing Protocols PDF

WEEK 10-11 TYPES OF ROUTING PROTOCOL NET102 – NETWORKING 2  At the end of the module, you should be able to: Explain a router as a computer with an Operating System and hardware....

WEEK 10-11 TYPES OF ROUTING PROTOCOL NET102 – NETWORKING 2  At the end of the module, you should be able to: Explain a router as a computer with an Operating System and hardware. Demonstrate the ability to configure devices and apply addresses. Explain how routers forward packets to the destination. Discuss Administrative Distance. Explain Switch 2960. 2 NET102 – NETWORKING 2  WEEK 10-11 ROUTING PROTOCOLS Routing Introduction A router can learn a route using one of two methods: 1. Static Routes A router can learn a static route in two ways: - First, a router will look at its active interfaces. This is commonly called a connected or directly connected route. - The second way that a router can learn a static route is for you to configure it manually. One special type of static route is called a default route, commonly called the gateway of last resort. 3 NET102 – NETWORKING 2  WEEK 10-11 ROUTING PROTOCOLS Routing Introduction 2. Dynamic Routes A router learns dynamic routes by running a routing protocol. Routing protocols will learn about routes from other neighboring routers running the same routing protocol. Routed and Routing Protocols 4 NET102 – NETWORKING 2  WEEK 10-11 ROUTING PROTOCOLS Dynamic Routing Protocols Dynamic routing protocols play an important role in today’s networks. The following sections describe several important benefits that dynamic routing protocols provide. In many networks, dynamic routing protocols are typically used with static routes. 5 NET102 – NETWORKING 2  WEEK 10-11 ROUTING PROTOCOLS The Evolution of Dynamic Routing Protocols 6 NET102 – NETWORKING 2  WEEK 10-11 ROUTING PROTOCOLS Role of Dynamic Routing Protocol What exactly are dynamic routing protocols? Routing protocols are used to facilitate the exchange of routing information between routers. Routing protocols allow routers to dynamically learn information about remote networks and automatically add this information to their own routing tables. Routing protocols determine the best path to each network, which is then added to the routing table. One of the primary benefits of using a dynamic routing protocol is that routers exchange routing information whenever there is a topology change. This exchange allows routers to automatically learn about new networks and also to find alternate paths if there is a link failure to a current network. Compared to static routing, dynamic routing protocols require less administrative overhead. However, the expense of using dynamic routing protocols is dedicating part of a router’s resources for protocol operation, including CPU time and network link bandwidth. Despite the benefits of dynamic routing, static routing still has its place. There are times when static routing is more appropriate and other times when dynamic routing is the better choice. More often than not, you will find a combination of both types of routing in any network that has a moderate level of complexity. 7 NET102 – NETWORKING 2  WEEK 10-11 ROUTING PROTOCOLS Network Discovery and Routing Table Maintenance Purpose of Dynamic Routing Protocols Discovering remote networks Maintaining up-to-date routing information Choosing the best path to destination networks Having the ability to find a new best path if the current path is no longer available The components of a routing protocol are as follows: Data structures Algorithm Routing protocol messages 8 NET102 – NETWORKING 2  WEEK 10-11 ROUTING PROTOCOLS Dynamic Routing Protocol Operation In general, the operations of a dynamic routing protocol can be described as follows: 1. The router sends and receives routing messages on its interfaces. 2. The router shares routing messages and routing information with other routers that are using the same routing protocol. 3. Routers exchange routing information to learn about remote networks. 4. When a router detects a topology change, the routing protocol can advertise this change to other routers. 9 NET102 – NETWORKING 2  WEEK 10-11 ROUTING PROTOCOLS Dynamic Routing Protocol Advantages 10 NET102 – NETWORKING 2  WEEK 10-11 ROUTING PROTOCOLS Static Routing Usage, Advantages, and Disadvantages Static routing has several primary uses, including the following: Providing ease of routing table maintenance in smaller networks that are not expected to grow significantly. Routing to and from stub networks. Using a single default route, used to represent a path to any network that does not have a more specific match with another route in the routing table. 11 NET102 – NETWORKING 2  WEEK 10-11 ROUTING PROTOCOLS Static Routing Usage, Advantages, and Disadvantages Static routing advantages are as follows: Minimal CPU processing Easier for administrator to understand Easy to configure Static routing disadvantages are as follows: Configuration and maintenance are time-consuming. Configuration is error-prone, especially in large networks. Administrator intervention is required to maintain changing route information. Does not scale well with growing networks; maintenance becomes cumbersome. Requires complete knowledge of the entire network for proper implementation 12 NET102 – NETWORKING 2  WEEK 10-11 ROUTING PROTOCOLS Dynamic Routing Advantages and Disadvantages Dynamic routing advantages are as follows: Administrator has less work in maintaining the configuration when adding or deleting networks. Protocols automatically react to the topology changes. Configuration is less error-prone. More scalable; growing the network usually does not present a problem. Dynamic routing disadvantages are as follows: Router resources are used (CPU cycles, memory, and link bandwidth). More administrator knowledge is required for configuration, verification, and troubleshooting. 13 NET102 – NETWORKING 2  WEEK 10-11 ROUTING PROTOCOLS Classifying Dynamic Routing Protocols Routing protocols can be classified into different groups according to their characteristics: IGP or EGP Distance vector or link-state Classful or classless The sections that follow discuss these classification schemes in more detail. 14 NET102 – NETWORKING 2  WEEK 10-11 ROUTING PROTOCOLS Classifying Dynamic Routing Protocols The most commonly used routing protocols are as follows: RIP: A distance vector interior routing protocol IGRP: The distance vector interior routing protocol developed by Cisco (deprecated from Cisco IOS Release 12.2 and later) OSPF: A link-state interior routing protocol IS-IS: A link-state interior routing protocol EIGRP: The advanced distance vector interior routing protocol developed by Cisco BGP: A path vector exterior routing protocol 15 NET102 – NETWORKING 2  WEEK 10-11 ROUTING PROTOCOLS Autonomous Systems Autonomous system (AS) otherwise known as a routing domain—is a collection of routers under a common administration. An autonomous system (AS) is a group of networks under a single administrative control, which could be your company, a division within your company, or a group of companies. An AS can provide distinct boundaries for a routing protocol, and thus provides some advantages. Interior gateway protocols (IGP) Exterior gateway protocols (EGP) Border Gateway Protocol (BGP) 16 NET102 – NETWORKING 2  WEEK 10-11 ROUTING PROTOCOLS IGP Versus EGP Routing Protocols 17 NET102 – NETWORKING 2  WEEK 10-11 ROUTING PROTOCOLS Distance Vector and Link-State Routing Protocols Distance vector routing protocols means that routes are advertised as vectors of distance and direction. Distance vector protocols work best in situations where: The network is simple and flat and does not require a hierarchical design. The administrators do not have enough knowledge to configure and troubleshoot links tate protocols. Specific types of networks, such as hub-and-spoke networks, are being implemented. Worst-case convergence times in a network are not a concern. 18 NET102 – NETWORKING 2  WEEK 10-11 ROUTING PROTOCOLS Distance Vector and Link-State Routing Protocols Link-State routing protocols uses the link-state information to create a topology map and to select the best path to all destination networks in the topology. Link-state protocols work best in situations where The network design is hierarchical, usually occurring in large networks. The administrators have a good knowledge of the implemented link-state routing protocol. Fast convergence of the network is crucial. 19 NET102 – NETWORKING 2  WEEK 10-11 ROUTING PROTOCOLS Classful and Classless Routing Protocols 20 NET102 – NETWORKING 2  WEEK 10-11 ROUTING PROTOCOLS Dynamic Routing Protocols and Convergence Convergence is when the routing tables of all routers are at a state of consistency. 21 NET102 – NETWORKING 2  WEEK 10-11 ROUTING PROTOCOLS Metrics 22 NET102 – NETWORKING 2  WEEK 10-11 ROUTING PROTOCOLS Metrics and Routing Protocols Metric Parameters 23 NET102 – NETWORKING 2  WEEK 10-11 ROUTING PROTOCOLS Metrics and Routing Protocols Metrics used in IP routing protocols include the following: Hop count Bandwidth Load Delay Reliability Cost 24 NET102 – NETWORKING 2  WEEK 10-11 ROUTING PROTOCOLS Metrics and Routing Protocols Metric Field in the Routing Table The list that follows defines the metric for each routing protocol: RIP: Hop count: Best path is chosen by the route with the lowest hop count. IGRP and EIGRP: Bandwidth, delay, reliability, and load: Best path is chosen by the route with the smallest composite metric value calculated from these multiple parameters. By default, only bandwidth and delay are used. IS-IS and OSPF: Cost: Best path is chosen by the route with the lowest cost. The Cisco implementation of OSPF uses bandwidth to determine the cost. IS-IS is discussed in CCNP. 25 NET102 – NETWORKING 2  WEEK 10-11 ROUTING PROTOCOLS Metric Field in the Routing Table 26 NET102 – NETWORKING 2  WEEK 10-11 ROUTING PROTOCOLS Metric Field in the Routing Table 27 NET102 – NETWORKING 2  WEEK 10-11 ROUTING PROTOCOLS Metrics and Routing Protocols Load Balancing across equal-cost paths 28 NET102 – NETWORKING 2  WEEK 10-11 ROUTING PROTOCOLS Administrative Distance Purpose of Administrative Distance Multiple Routing Sources Administrative distance (AD) defines the preference of a routing source. Each routing source —including specific routing protocols, static routes, and even directly connected networks —is prioritized in order of most to least preferable using an administrative distance value. 29 NET102 – NETWORKING 2  WEEK 10-11 ROUTING PROTOCOLS Administrative Distance Purpose of Administrative Distance Cisco routers use the AD feature to select the best path when they learn about the same destination network from two or more different routing sources. Administrative distance is an integer value from 0 to 255. The lower the value, the more preferred the route source. An administrative distance of 0 is the most preferred. Only a directly connected network has an administrative distance of 0, which cannot be changed. An administrative distance of 255 means the router will not believe the source of that route, and it will not be installed in the routing table. 30 NET102 – NETWORKING 2  WEEK 10-11 ROUTING PROTOCOLS Comparing Administrative Distances 31 NET102 – NETWORKING 2  WEEK 10-11 ROUTING PROTOCOLS Comparing Administrative Distances 32 NET102 – NETWORKING 2  WEEK 10-11 ROUTING PROTOCOLS Comparing Administrative Distances 33 NET102 – NETWORKING 2  WEEK 10-11 ROUTING PROTOCOLS Dynamic Routing Protocols and Administrative Distance 34 NET102 – NETWORKING 2  WEEK 10-11 ROUTING PROTOCOLS Default Administrative Distances 35 NET102 – NETWORKING 2  WEEK 10-11 ROUTING PROTOCOLS Static Routes and Administrative Distance 36 NET102 – NETWORKING 2  WEEK 10-11 ROUTING PROTOCOLS Static Routes and Administrative Distance 37 NET102 – NETWORKING 2  WEEK 10-11 ROUTING PROTOCOLS Directly Connected Networks and Administrative Distance 38 NET102 – NETWORKING 2  WEEK 10-11 ROUTING PROTOCOLS Directly Connected Networks and Administrative Distance 39 NET102 – NETWORKING 2 40