Introduction to Dynamic Routin g Protocol g Routing Protocols and Concepts – Chapter 3 © 2007 Cisco Systems, Inc. All rights reserved. Cisco Public ITE PC v4.0 Chapter 1 1 Objectives  D esc ri be th e r o l e o f dy n a mi c r ou tin g p r o t oco l s a n d escbe eoeodya cou gpoocosad 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 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. ITE PC v4.0 Chapter 1 2 © 2007 Cisco Systems, Inc. All rights reserved. Cisco Public Dynamic Routing Protocols  D y n a mi c r ou tin g p r o t oco l s a r e usua ll y y a c ou g p o oco s a e usua y used in larger networks to ease the administrative and operational overhead fi ltti t o f us i ng on l y s t a ti c rou t es.  Typically, a network uses a combination f b th d i ti t l d o f b o th a d ynam i c rou ti ng pro t oco l an d static routes. ITE PC v4.0 Chapter 1 3 © 2007 Cisco Systems, Inc. All rights reserved. Cisco Public The Evolution of Dynamic Routing Protocols  One of the earliest routing protocols was Routing Information Protocol (RIP). RIP h l d i t i RIP 2 H – RIP h as evo l ve d i n t o a newer vers i on RIP v 2 . H owever, –The newer version of RIP still does not scale to larger network implementations.  To address the needs of larger networks, two advanced routing protocols were developed: Open Shortest Path First (OSPF) and Intermediate System-to- It dit S t (IS IS) I n t erme di a t e S ys t em (IS - IS) .  Cisco developed Interior Gateway Routing Protocol (IGRP) and Enhanced IGRP (EIGRP), which also scales well in larger network implementations.  Additionally there was the need to interconnect different internetworks and provide  Additionally , there was the need to interconnect different internetworks and provide routing among them. Border Gateway Routing (BGP) protocol is now used between ISPs as well as between ISPs and their larger private clients to exchange routing information.  With the advent of numerous consumer devices using IP the IPv4 addressing space  With the advent of numerous consumer devices using IP , the IPv4 addressing space is nearly exhausted. Thus IPv6 has emerged. To support the communication based on IPv6, newer versions of the IP routing protocols have been developed (see the IPv6 row in the table). ITE PC v4.0 Chapter 1 4 © 2007 Cisco Systems, Inc. All rights reserved. Cisco Public 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 Determine best path to a destination . –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 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. – One of the primary benefits to using a dynamic routing protocol is that routers exchange routing information whenever there is a topology change. This exchange ll t t t ti ll l b t t k d l t fi d lt t a ll ows rou t ers t o au t oma ti ca ll y l earn a b ou t new ne t wor k s an d a l so t o fi n d a lt erna t e paths when there is a link failure to a current network. ITE PC v4.0 Chapter 1 5 © 2007 Cisco Systems, Inc. All rights reserved. Cisco Public Dynamic Routing Protocols  D esp it e th e be n e fit s o f dy n a mi c r ou tin g, s t a ti c r ou tin g s till esp e e be e s o dy a c ou g, s a c ou g s has its place.  There are times when static routing is more appropriate and 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 More often than not , you will find a combination of both types of routing in any network that has a moderate level of complexity. ITE PC v4.0 Chapter 1 6 © 2007 Cisco Systems, Inc. All rights reserved. Cisco Public Dynamic Routing Protocols  A routin g p rotocol gp –is a set of processes, algorithms, and messages that are used to exchange routing information and populate the routing table with the routin g p rotocol's choice of best p aths gp p  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 Abilit t fi d b t th if th t th i l il bl - Abilit y t o fi n d a new b es t pa th if th e curren t pa th i s no l onger ava il a bl e ITE PC v4.0 Chapter 1 7 © 2007 Cisco Systems, Inc. All rights reserved. Cisco Public Dynamic Routing Protocols Dynamic Routing Protocols  Components of a routing protocol – Data structures Data structures •Some routing protocols use tables and/or databases for its operations. This information is kept in RAM Al ith – Al gor ith m •Algorithm is a finite list of steps used in accomplishing a task • Algorithms are used for facilitating routing information and best path Algorithms are used for facilitating routing information and best path determination –Routing protocol messages Th f di i i hb d hf • Th ese are messages f or di scover i ng ne i g hb ors an d exc h ange o f routing information , and other tasks to learn and maintain accurate information about the network. ITE PC v4.0 Chapter 1 8 © 2007 Cisco Systems, Inc. All rights reserved. Cisco Public Dynamic Routing Protocol Operation Dynamic Routing Protocol Operation  All routing protocols have the same purpose - to learn about remote networks and to quickly adapt whenever there is a change in the topology.  The method that a routing protocol uses to accomplish this depends upon the algorithm it uses and the operational characteristics of that protocol.  In general the operations of a dynamic routing protocol can be described as  In general , the operations of a dynamic routing protocol can be described as follows: –The router sends and receives routing messages on its interfaces. – The router shares routing messages and routing information with other routers that are using the same routing protocol. –Routers exchange routing information to learn about remote networks. – When a router detects a topology change the routing protocol can advertise this change to other routers. ITE PC v4.0 Chapter 1 9 © 2007 Cisco Systems, Inc. All rights reserved. Cisco Public Dynamic Routing Protocols  Advantages of static routing It b k lti l  Advantages of dynamic routing - It can b ac k up mu lti p l e interfaces/networks on a router -Minimal CPU processing Easier for administrator to -Administrator has less work maintaining the configuration when adding or deleting networks. - Easier for administrator to understand -Easy to configure - No extra resources are needed -Protocols automatically react to the topology changes. -Confi g uration is less erro r -prone. No extra resources are needed -More secure  Disadvantages of static routing g -More scalable, growing the network usually does not present a problem  Disadvantages of dynamic routing -Network changes require manual reconfiguration -Configuration and maintenance is time - consuming  Disadvantages of dynamic routing -Router resources are used (CPU cycles, memory and link bandwidth). time consuming -Does not scale well in large topologies -Confi g uration is erro r - p rone , -More administrator knowledge is required for configuration, verification, and troubleshooting. ITE PC v4.0 Chapter 1 10 © 2007 Cisco Systems, Inc. All rights reserved. Cisco Public g p, especially in large networks [...]... 12 Classifying Routing Protocols Dynamic routing protocols: –RIP •A distance vector interior routing protocol –IGRP •The distance vector interior routing developed by Cisco (deprecated from 12.2 IOS and later) –EIGRP •The advanced distance vector interior routing protocol developed by Cisco –OSPF OSPF •A link-state interior routing protocol –IS-IS •A link-state interior routing protocol –BGP •A path... figure, network 172.16 .3. 0 is two hops, hops or two routers away away –EIGRP uses a combination of bandwidth and delay, –OSPF uses bandwidth (cost) OSPF ITE PC v4.0 Chapter 1 © 2007 Cisco Systems, Inc All rights reserved Cisco Public 23 Routing Protocols Metrics Metrics used in IP routing protocols –Bandwidth •Influences path selection by preferring the path with the highest bandwidth –Cost Cost •A value... paths, and update th i routing i f ti l l t best th d d t their ti tables Routing R ti protocols can b rated b t l be t d based on d the speed to convergence; the faster the convergence, the better the routing protocol t l –RIP and IGRP are slow to converge –EIGRP and OSPF are faster to converge EIGRP ITE PC v4.0 Chapter 1 © 2007 Cisco Systems, Inc All rights reserved Cisco Public 22 Routing Protocols. .. clasasfull network You can still subnet it but can only do it once and all it, network needs to have the identical mask – Routing protocols such as RIPv1 and IGRP Classless routing protocols gp –Do send subnet mask in routing updates –support variable length subnet masks (VLSM) •In the figure, the classless version of the network is g , using both /30 and /27 masks in the same topology •Tony: It means you can... exterior routing p p g protocol ITE PC v4.0 Chapter 1 © 2007 Cisco Systems, Inc All rights reserved Cisco Public 13 Classifying Routing Protocols An autonomous system (AS) - otherwise known as a routing domain - is a collection of routers under a common administration Because the Internet is based on the ASs concept, two types of routing protocols are required: interior and exterior routing protocols. .. ITE PC v4.0 Chapter 1 © 2007 Cisco Systems, Inc All rights reserved Cisco Public 19 Classifying Routing Protocols Comparison of Distance Vector & Link State Routing Protocols Distance vector protocols work Di t t t l k best in situations where: –The network is simple and flat p and does not require a special hierarchical design –The administrators do not have enough knowledge to configure and troubleshoot... being implemented –Worst-case convergence times in a network are not a concern ITE PC v4.0 Chapter 1 © 2007 Cisco Systems, Inc All rights reserved Cisco Public 20 Classifying Routing Protocols Classful routing protocols –Do NOT send subnet mask in routing updates Do updates, –Do NOT support VLSM, –Classful routing protocols cannot be used when a network is subnetted using more than one g subnet mask,... troubleshoot link-state protocols Link-state protocols work best in situations where: –The network design is hierarchical, g , usually occurring in large networks –The administrators have a good knowledge of the implemented linklink state routing protocol –Fast convergence of the network is crucial crucial –Specific types of networks, such as hub -and- spoke networks, are being implemented –Worst-case convergence... rights reserved Cisco Public 24 Routing Protocols Metrics 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) Refer to the example in the figure The routers are using the RIP routing protocol –The metric associated with... determination – incomplete view of network topology topology •Distance vector protocols use routers as sign posts along the path to the final destination •Distance vector routing p g protocols do not have an actual map of the network topology – Generally, periodic updates •Some distance vector protocols periodically send complete routing tables to all connected neighbors ITE PC v4.0 Chapter 1 © 2007 . Introduction to Dynamic Routin g Protocol g Routing Protocols and Concepts – Chapter 3 © 2007 Cisco Systems, Inc. All rights reserved. Cisco Public ITE PC v4.0 Chapter 1 1 Objectives  D esc ri be . a dynamic routing protocol can be described as follows: –The router sends and receives routing messages on its interfaces. – The router shares routing messages and routing information. v4.0 Chapter 1 12 © 2007 Cisco Systems, Inc. All rights reserved. Cisco Public gy Classifying Routing Protocols  Dynamic routing protocols: –RIP •A distance vector interior routing protocol – IGRP •The