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Introduction to Dynamic Routing Protocol

Introduction to Dynamic Routing Protocol. Routing Protocols and Concepts – Chapter 3 Sandra Coleman, CCNA, CCAI. 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.

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Introduction to Dynamic Routing Protocol

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  1. Introduction to Dynamic Routing Protocol Routing Protocols and Concepts – Chapter 3 Sandra Coleman, CCNA, CCAI

  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. Overview of dynamic routing protocols

  4. Dynamic Routing Protocols • Function(s) of Dynamic Routing Protocols: • -Dynamically share information between routers. • -Automatically update routing table when topology changes. • -Determine best path to a destination.

  5. Dynamic Routing Protocols • 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 • -They can NOW SHARE information with each other!

  6. Dynamic Routing Protocols • Components of a routing protocol • 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

  7. Dynamic Routing Protocols • Advantages of static routing • -It can backup multiple interfaces/networks on a router • -Easy to configure • -No extra resources are needed • -More secure • -Administrator maintains control over the routing process • Disadvantages of static routing • -Network changes require manual reconfiguration • -Does not scale well in large topologies

  8. Classifying Routing Protocols • Dynamic routing protocols are grouped according to characteristics. Examples include: • -RIP • -IGRP • -EIGRP • -OSPF • -IS-IS • -BGP • Autonomous System is a group of routers under the control of a single authority.

  9. Classifying Routing Protocols • Types of routing protocols: • -Interior Gateway Protocols (IGP) – routing within an AS • -Exterior Gateway Protocols (EGP) – routing between AS’s

  10. Classifying Routing Protocols • 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

  11. IGP Protocols • Distance vector (RIP, EIGRP) • routes are advertised as vectors of distance & direction. • incomplete view of network topology. (only sees its neighbors) • Generally, periodic updates. (30-, 90-seconds, etc.) are sent ONLY to neighboring routers • Work best in a simple, flat network or a hub-and-spoke topology • Admins do NOT have to be very knowledgable • Link state (OSPF) • complete view of network topology is created. (Sees EVERYONE – like a map) • Knowledgeable administrators • updates are not periodic. (triggered by a change) • Quicker convergence • Should be used in larger organizations with more than 5 routers (especially if some of them are NOT Cisco routers)

  12. Classifying Routing Protocols • Classful routing protocols • Do NOT send subnet mask in routing updates • DO NOT support VLSM • RIPv1 and IGRP • Classless routing protocols • DO send subnet mask in • routing updates. • Supports VLSM • RIPv2, EIGRP, OSPF, IS-IS, BGP

  13. Classifying Routing Protocols • Convergenceis defined as when all routers’ routing tables are at a state of consistency (They all have the SAME level of knowledge)

  14. Convergence • Fast convergence is VERY desirable, especially when using dynamic routing protocols. • WHY? Routers could make incorrect forwarding decisions if the topology is NOT converged.

  15. Routing Protocols Metrics • Metric • A value used by a routing protocol to determine whichroutes are better than others. • See the RIP example below!

  16. Routing Protocols Metrics • Metrics used in IP routing protocols • -Bandwidth – Highest preferred (EIGRP) • -Cost – value determined by IOS or by network admin. • -Delay – time to traverse a path • -Hop count - # routers packet must pass through (RIP) • -Load – traffic utilization on a certain link • -Reliability – probability of a link failure (based on an algorithm) • You don’t need to understand all of these right now, we’ll discuss them as we get to the protocol they apply to.

  17. Metric Example

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

  19. What if multiple paths have same metric? • Both are placed in the routing table and packets are balanced between the 2. To see if it is in effect, just look at the routing table. • Load balancing • This is the ability of a router to distribute packets among multiple same cost paths

  20. Administrative Distance of a Route • Purpose of Administrative Distance • It’s a numeric value that specifies the trustworthiness of a route. Uses AD to select the best path when it learns about the same destination network from 2 or more different routing sources. • Route with lowest AD is the one chosen for the routing table (Best path)

  21. Administrative Distance of a Route • Identifying the Administrative Distance (AD) in a routing table • It is the first number in the brackets in the routing table

  22. Administrative Distance of a Route • Dynamic Routing Protocols – the lower the number, the more trustworthy the route!

  23. Administrative Distance of a Route • Directly connected routes • Have a default AD of 0 • Static Routes • Administrative distance of a static route has a default value of 1 • To see the AD of a static route, use the command below:

  24. Administrative Distance of a Route • Directly connected routes • -Immediately appear in the routing table as soon as the interface is configured and the lines are brought up – that is the IP address is assigned to an interface! These routes have an AD of 0.

  25. Ch. 3…Dynamic Routing Protocols is finished • Study Guide – • Pg. 139 – Matching • Pg. 142 –Dynamic Routing Protocols Classification Chart • Pg. 144-145 – Metric Parameters Exercise • Pg. 146 – Routing Sources & AD Exercise • Pg. 146-147 – Identifying Elements of a routing table • Labs - • Packet Tracer Skills Integration Challenge TODAY! • Test on Ch. 3 will be Monday, Feb. 11, 2013 – NO HANDS ON! Just lecture notes.. MC, Tables to fill in, Interpreting the routing table. • If you don’t get through with the labs today, you can finish them over the weekend. • Online test for Ch. 3 – will be on until Sunday night, Feb. 10, 2013, midnight!

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