Presentation on theme: "Routing and Routing Protocols Last Update"— Presentation transcript:
1 Routing and Routing Protocols Last Update 2009.07.17 1.5.0 Copyright Kenneth M. Chipps Ph.D.
2 Copyright 2005-2009 Kenneth M. Chipps Ph.D. www.chipps.com ObjectivesCopyright Kenneth M. Chipps Ph.D.
3 Routing Tables Population For the router to be able to handle arriving frames, entries must be made into the routing tableEntries in a routing table can be generated in three waysDirectly connected routesStatic routesDynamic routesCopyright Kenneth M. Chipps Ph.D.
4 Directly Connected Routes When a data line existsWhen a cable is connected between the demarc of that data line and an interface of the routerWhen the data line is activeWhen the interface on the router is activatedA directly connected route is added to the routing tableCopyright Kenneth M. Chipps Ph.D.
5 Directly Connected Routes Copyright Kenneth M. Chipps Ph.D.
6 Copyright 2005-2009 Kenneth M. Chipps Ph.D. www.chipps.com Static RoutesWhen the administrator uses the ip route command to add a route to the routing tableStatic routes are used whenThe internetwork is small, may seldom change, or has no redundant linksThe routers need to use dial backup to dynamically call another router when a leased line failsCopyright Kenneth M. Chipps Ph.D.
7 Copyright 2005-2009 Kenneth M. Chipps Ph.D. www.chipps.com Static RoutesAn enterprise internetwork has many small branch offices, each with only one possible path to reach the rest of the internetworkAn enterprise wants to forward packets to hosts in the Internet, not to hosts in the enterprise networkCopyright Kenneth M. Chipps Ph.D.
8 Result of Using a Static Route Copyright Kenneth M. Chipps Ph.D.
9 Result of Using a Static Route Copyright Kenneth M. Chipps Ph.D.
10 Copyright 2005-2009 Kenneth M. Chipps Ph.D. www.chipps.com Dynamic RoutesWhen a routing protocol is activated on the routerWhen other routers running the same routing protocol talk to each otherThen the routes know by the other routers are added to the routing table as dynamic routesCopyright Kenneth M. Chipps Ph.D.
11 Copyright 2005-2009 Kenneth M. Chipps Ph.D. www.chipps.com Routing Table EntriesThe command show ip route shows the routing tableEach of these methods of entering routes in the routing table has an indicator associated with itC for directly connected networksS for static routesR for routes learned through the RIP routing protocol as an example of a dynamic routeCopyright Kenneth M. Chipps Ph.D.
12 Two Ways to Look at Protocols Routing ProtocolsRouted ProtocolsCopyright Kenneth M. Chipps Ph.D.
13 What is a Routing Protocol These are network layer protocols that are responsible for path determination and traffic switchingThese have to do with the actual routes the packets take and how that path is calculatedThese protocols include RIP, EIGRP, OSPF, IS-IS, and BGPCopyright Kenneth M. Chipps Ph.D.
14 What is a Routing Protocol Copyright Kenneth M. Chipps Ph.D.
15 What is a Routed Protocol These protocols are routed by the routing protocolsThey are concerned with the construction and transport of the data itself regardless of how it arrives at its destinationWhen the OSI model talks about encapsulation, this is what it is referring toCopyright Kenneth M. Chipps Ph.D.
16 What is a Routed Protocol These cover all 7 layers of the OSI modelThese protocols contain enough information in the fields in their headers that allow the packet to be routed from one network to another by the routing protocolCopyright Kenneth M. Chipps Ph.D.
17 What is a Routed Protocol Copyright Kenneth M. Chipps Ph.D.
18 Static v Dynamic Routing Static routes, as we will see, are entered from the keyboard and do not require routing protocolsDynamic routes are created by routing protocolsCopyright Kenneth M. Chipps Ph.D.
19 Static v Dynamic Routing Static routing consists of entries made into the routing table in the router by the network administrator prior to the beginning of routingThese entries do not change unless the network administrator alters themCopyright Kenneth M. Chipps Ph.D.
20 Static v Dynamic Routing This method works well in environments where network traffic is relatively predictable and where network design is relatively simpleBecause static routing systems cannot react to network changes, they generally are considered unsuitable for today's large, changing networksCopyright Kenneth M. Chipps Ph.D.
21 Static v Dynamic Routing Whereas dynamic routing protocols can adjust to changing network circumstances by analyzing incoming routing update messagesIf the message indicates that a network change has occurred, the routing software recalculates routes and sends out new routing update messagesCopyright Kenneth M. Chipps Ph.D.
22 Static v Dynamic Routing These messages permeate the network, stimulating routers to rerun their algorithms and change their routing tables accordinglyCopyright Kenneth M. Chipps Ph.D.
23 Static v Dynamic Routing Copyright Kenneth M. Chipps Ph.D.
24 Static v Dynamic Routing Copyright Kenneth M. Chipps Ph.D.
25 Dynamic Routing Protocols Dynamic routing protocols usually have one or more of the following design goalsOptimalityLow overheadRobustnessFlexibilityRapid convergenceCopyright Kenneth M. Chipps Ph.D.
26 Routing Protocol Optimality Optimality refers to the capability of the routing protocol to select the best route, which depends on the metrics and metric weightings used to make the calculationCopyright Kenneth M. Chipps Ph.D.
27 Routing Protocol Overhead Low overhead refers to simple and efficient overheadCopyright Kenneth M. Chipps Ph.D.
28 Routing Protocol Robustness Routing protocols must be robust, which means that they should perform correctly in the face of unusual or unforeseen circumstances, such as hardware failures, high load conditions, and incorrect implementationsCopyright Kenneth M. Chipps Ph.D.
29 Routing Protocol Flexibility Routing protocols should also be flexible, which means that they should quickly and accurately adapt to a variety of network circumstancesAssume, for example, that a network segment has gone downAs they become aware of the problem, many routing protocols will quickly select the next-best path for all routes normally using that segmentCopyright Kenneth M. Chipps Ph.D.
30 Routing Protocol Convergence Routing protocols must converge rapidly, which is a process of agreement, by all routers, on optimal routesWhen a network event causes routes either to go down or become available, routers distribute routing update messages that permeate networks, stimulating recalculation of optimal routes and eventually causing all routers to agreeCopyright Kenneth M. Chipps Ph.D.
31 Routing Protocol Convergence Routing protocols that converge slowly can cause routing loops or network outagesAn example of the need for rapid convergence is seen in the use of distance vector protocolsRouters using routing protocols based on the distance vector method receive their neighbor’s routing tableCopyright Kenneth M. Chipps Ph.D.
32 Routing Protocol Convergence Using this they build a network mapThis approach to learning can cause problems such as routing loops and counts to infinityRouting loops can occur if the internetwork is slow to converge on a new configuration after a route failsThis situation will produce inconsistent entries in the router tablesCopyright Kenneth M. Chipps Ph.D.
33 Dynamic Routing Protocols Let’s organize the different types of routing protocols and then discuss each oneCopyright Kenneth M. Chipps Ph.D.
34 Dynamic Routing Protocols Intradomain or InteriorInterdomain or ExteriorDistance VectorLink StatePath VectorStandardProprietaryHELLO 1IGRP1OSPFNLSP1EGP1RIP V11EIGRPIS-ISBGPRIP V21 No Longer UsedCopyright Kenneth M. Chipps Ph.D.
35 Copyright 2005-2009 Kenneth M. Chipps Ph.D. www.chipps.com No Longer UsedHELLOThe original NSFnet backbone consisted of six Digital Equipment Corporation LSI-11 computers located across the United StatesThese computers ran special software colloquially called fuzzball that enabled them to function as routersThese fuzzball routers connected various networks to the NSFnet and the ARPAnetCopyright Kenneth M. Chipps Ph.D.
36 Copyright 2005-2009 Kenneth M. Chipps Ph.D. www.chipps.com No Longer UsedThe six NSFnet routers worked as an autonomous system and like any AS, used an interior routing protocol to exchange routing informationThe routing protocol used in these early routers was called the HELLO protocolIt was developed in the early 1980s and documented in RFC 891 published December 1983Copyright Kenneth M. Chipps Ph.D.
37 Copyright 2005-2009 Kenneth M. Chipps Ph.D. www.chipps.com No Longer UsedThe name HELLO is capitalized, but is not an acronym; it simply refers to the word hello, since the protocol uses messages that are sort of analogous to the routers talking to each otherThe HELLO protocol uses a distance-vector algorithm, like the RIPUnlike RIP, HELLO does not use hop count as a metricCopyright Kenneth M. Chipps Ph.D.
38 Copyright 2005-2009 Kenneth M. Chipps Ph.D. www.chipps.com No Longer UsedInstead, it attempts to select the best route by assessing network delays and choosing the path with the shortest delayOne of the key jobs of routers using HELLO is to compute the time delay to send and receive datagrams to and from its neighborsOn a regular basis, routers exchange HELLO messages that contain clock and timestamp informationCopyright Kenneth M. Chipps Ph.D.
39 Copyright 2005-2009 Kenneth M. Chipps Ph.D. www.chipps.com No Longer UsedBy comparing the clock value and timestamp in the message to its own clock using a special algorithm, a receiving device can compute an estimate for the amount of time it takes to send a datagram over the linkHELLO messages also contain routing information in the form of a set of destinations that the sending router is able to reach and a metric for eachCopyright Kenneth M. Chipps Ph.D.
40 Copyright 2005-2009 Kenneth M. Chipps Ph.D. www.chipps.com No Longer UsedHowever in this case, the metric is an estimate of the round-trip delay cost for each destinationThis information is added to the computed round-trip delay time for the link over which the message was received, and used to update the receiving router's own routing tableCopyright Kenneth M. Chipps Ph.D.
41 Copyright 2005-2009 Kenneth M. Chipps Ph.D. www.chipps.com No Longer UsedRIP Version1This version of RIP only supports FLSM based on address classesAs address classes no longer exist version 1 is uselessCopyright Kenneth M. Chipps Ph.D.
42 Copyright 2005-2009 Kenneth M. Chipps Ph.D. www.chipps.com No Longer UsedIGRPWith the deployment of EIGRP and OSPF there is no longer any need for IGRPTherefore, no one uses it any longerCopyright Kenneth M. Chipps Ph.D.
43 Copyright 2005-2009 Kenneth M. Chipps Ph.D. www.chipps.com No Longer UsedNLSPNLSP - NetWare Link Services Protocol is a link-state routing protocol in the Novell NetWare architectureNLSP is based on the OSI IS-IS or Intermediate System-to-Intermediate System protocol and was designed to replace IPX RIP and SAP, Novell's original routing protocols that were designed for small scale internetworksCopyright Kenneth M. Chipps Ph.D.
44 Copyright 2005-2009 Kenneth M. Chipps Ph.D. www.chipps.com No Longer UsedCompared to RIP and SAP, NLSP provides improved routing, better efficiency, and scalabilityAs no one uses NetWare anymore, no one uses NLSP any longerCopyright Kenneth M. Chipps Ph.D.
45 Copyright 2005-2009 Kenneth M. Chipps Ph.D. www.chipps.com No Longer UsedEGPEGP – Exterior Gateway Protocol was the first routing protocol used to allow autonomous systems to talk to each otherIt was developed in 1982 by Eric C. Rosen and David L. MillsIt was first formally described in RFC 827 and formally specified in RFC 904 in 1984EGP is no longer usedCopyright Kenneth M. Chipps Ph.D.
46 Copyright 2005-2009 Kenneth M. Chipps Ph.D. www.chipps.com No Longer UsedBGP - Border Gateway Protocol is now the accepted standard for Internet routing and has essentially replaced the more limited EGPCopyright Kenneth M. Chipps Ph.D.
47 Interior and Exterior Protocols What is the difference between the various classes of routing protocolsWhere are exterior and interior protocols usedCopyright Kenneth M. Chipps Ph.D.
48 Interior and Exterior Protocols Copyright Kenneth M. Chipps Ph.D.
49 Interior and Exterior Protocols Copyright Kenneth M. Chipps Ph.D.
50 Interior and Exterior Protocols Copyright Kenneth M. Chipps Ph.D.
51 Intradomain v Interdomain Some routing protocols work only within domainsOthers work between domainsA domain in these terms is an autonomous system, which is a group of routers under a single administrative controlCopyright Kenneth M. Chipps Ph.D.
52 Intradomain v Interdomain The nature of these two types of routing protocols is differentIn that the intradomain routing protocols are concerned with talking to only their close relativesWhereas interdomain routing protocols are concerned with talking to strangersCopyright Kenneth M. Chipps Ph.D.
53 Intradomain v Interdomain Using these two types enables the organization to control the type and amount of outside traffic that comes in and goes out of its networkThe terms are also expressed as interior – intradomain and exterior – interdomainCopyright Kenneth M. Chipps Ph.D.
54 Intradomain v Interdomain Copyright Kenneth M. Chipps Ph.D.
55 Distance Vector Protocols A distance vector protocol is so named because its routes are advertised as vectors - distance and direction - where distance is defined in terms of a metric and direction is defined in terms of the next hop routerThese, known as Bellman-Ford protocols, call for each router to send all or some its routing table, but only to its neighborsCopyright Kenneth M. Chipps Ph.D.
56 Distance Vector Protocols In this arrangement each router depends on its neighbors for information, which its neighbors may have learned from their neighbors, and so onAn individual router has no way of knowing if the information in the routing table it receives is accurateThese routers just believe everything they hearCopyright Kenneth M. Chipps Ph.D.
57 Distance Vector Protocols As such distance vector routing protocols are sometimes referred to as routing by rumorA typical distance vector routing protocol uses a routing algorithm in which routers periodically send routing updates to all neighbors by broadcasting their entire routing tableCopyright Kenneth M. Chipps Ph.D.
58 Distance Vector Protocols In this case periodically means to transmit on a regular scheduleNeighbors are those routers at the other end of a data lineThe originating router sends its update to this neighborIt expects the neighbor to send the information on to that router's neighbors, and so onCopyright Kenneth M. Chipps Ph.D.
59 Distance Vector Protocols This update includes everything the router knowsIn other words its entire routing table with a few exceptions is sent outCopyright Kenneth M. Chipps Ph.D.
60 Copyright 2005-2009 Kenneth M. Chipps Ph.D. www.chipps.com Link State ProtocolsThe information that a distance vector protocol has available has been likened to a road signThat is it is just one more step on the journeyWhereas the information available to a link state protocol is more like a road mapCopyright Kenneth M. Chipps Ph.D.
61 Copyright 2005-2009 Kenneth M. Chipps Ph.D. www.chipps.com Link State ProtocolsA link state routing protocol cannot be easily fooled into making a bad routing decision because - with the map - it has a complete picture of the networkThis is because link state routers have first hand information from all of their peer routers, those that speak the same routing protocolCopyright Kenneth M. Chipps Ph.D.
62 Copyright 2005-2009 Kenneth M. Chipps Ph.D. www.chipps.com Link State ProtocolsEach of these routers originates information about itself, its directly connected links, and the state of those linksThis information is passed around from router to router, each router making a copy, but no router changing the informationHow does this all workCopyright Kenneth M. Chipps Ph.D.
63 Copyright 2005-2009 Kenneth M. Chipps Ph.D. www.chipps.com Link State ConceptsCopyright Kenneth M. Chipps Ph.D.
64 Copyright 2005-2009 Kenneth M. Chipps Ph.D. www.chipps.com Link State ProtocolsLike thisEach router establishes a relationship - an adjacency - with each of its neighborsEach router sends link state advertisements to each neighborOne link state advertisement is created for each of the router's links, identifying the link, the state of the link, the metric cost of the link, and the neighbors that are connected to the linkCopyright Kenneth M. Chipps Ph.D.
65 Copyright 2005-2009 Kenneth M. Chipps Ph.D. www.chipps.com Link State ProtocolsEach router receiving this information in turns forwards it to its neighborsEach router stores the link state advertisements it has received in a databaseSince all routers receive all link state advertisements, all routers have the same informationThe algorithm for the routing protocol is then applied to the information in the link state database to create a routing tableCopyright Kenneth M. Chipps Ph.D.
66 Copyright 2005-2009 Kenneth M. Chipps Ph.D. www.chipps.com Dijkstra AlgorithmLink-state protocols use the Dijkstra SPF - Shortest Path First algorithm to calculate and add routes to the IP routing tableThe SPF algorithm calculates all the possible routes to each destination network, and the cumulative metric for the entire pathCopyright Kenneth M. Chipps Ph.D.
67 Copyright 2005-2009 Kenneth M. Chipps Ph.D. www.chipps.com Dijkstra AlgorithmEach router views itself as the starting point, and each subnet as the destination, and use the SPF algorithm to look at the LSDB - Link State Database to create a roadmap and pick the best route to each subnetCopyright Kenneth M. Chipps Ph.D.
68 Characteristics of Link State The main features of link-state routing protocolsAll routers learn the same detailed information about the states of all the router links in the internetworkThe individual pieces of topology information are called LSAs, with all LSAs stored in RAM in the LSDBCopyright Kenneth M. Chipps Ph.D.
69 Characteristics of Link State Routers flood LSAs when they are created, on a regular but long time interval if the LSAs do not change over time, and immediately when an LSA changesThe LSDB does not contain routes, but it does contain information that can be processed by the Dijkstra SPF algorithm to find a router’s best routesCopyright Kenneth M. Chipps Ph.D.
70 Characteristics of Link State Each router runs the SPF algorithm, with the LSDB as input, resulting in the best - lowest cost - routes being added to the IP routing tableLink-state protocols converge quickly by immediately reflooding LSAs and rerunning the SPF algorithmCopyright Kenneth M. Chipps Ph.D.
71 Characteristics of Link State Link-state protocols consume much more RAM and CPU than do distance vector routing protocolsIf the internetwork changes a lot, link-state protocols can also consume much more bandwidth due to the relative to distance vector protocols large number of bytes of information in each LSACopyright Kenneth M. Chipps Ph.D.
72 Copyright 2005-2009 Kenneth M. Chipps Ph.D. www.chipps.com Routing MetricsRouting protocols use metrics to determine the best or optimal routeThe following metrics are often usedPath LengthReliabilityDelayBandwidthLoadCostCopyright Kenneth M. Chipps Ph.D.
73 Copyright 2005-2009 Kenneth M. Chipps Ph.D. www.chipps.com Routing MetricsCopyright Kenneth M. Chipps Ph.D.
74 Routing Metric Components Copyright Kenneth M. Chipps Ph.D.
75 Example Routing Metrics Copyright Kenneth M. Chipps Ph.D.
76 Administrative Distance A single router may learn routes from many different sourcesFor example, from static routes and from running multiple routing protocolsWhen a router learns more than one route to the same subnet, from different sources, the router needs to decide which route is best and then add that route to the IP routing tableCopyright Kenneth M. Chipps Ph.D.
77 Administrative Distance Because each routing protocol uses a different metric, a router cannot use the metric to determine which route is the best routeWhen choosing between multiple routes to the same destination but learned from different sources, the router picks the route with the lowest administrative distanceCopyright Kenneth M. Chipps Ph.D.
78 Administrative Distance The administrative distance is a number assigned to all the possible sources of routing information, routing protocols and static routes includedCopyright Kenneth M. Chipps Ph.D.
79 Default Distance Values Copyright Kenneth M. Chipps Ph.D.
80 Administrative Distance The administrative distance is shown by issuing the show ip route commandThe show ip route command output lists the administrative distance for most routes, with the notable exception of connected routes, which default to an administrative distance of 0The example shown next shows the output of the show ip route rip commandCopyright Kenneth M. Chipps Ph.D.
81 Administrative Distance The output highlights the administrative distance for the one RIP route known on router R1, which defaults to RIP’s setting of 120Copyright Kenneth M. Chipps Ph.D.
82 Administrative Distance Copyright Kenneth M. Chipps Ph.D.
83 Multiple Equal Cost Routes A single router may learn several routes to the same subnet, but the metrics may tieThese routes are typically called equal-cost routesWhen this occurs, the router uses the following logic to choose which route to add to its routing tableCopyright Kenneth M. Chipps Ph.D.
84 Multiple Equal Cost Routes It can add up to four of the routes to the routing table, which is the defaultThe number of equal-cost routes added to the routing table can be changed to between one and six by using the maximum-path number command as a subcommand of the routing protocolAfter routes are added to the routing table, the router then load-balances the traffic over various routesCopyright Kenneth M. Chipps Ph.D.
85 Multiple Equal Cost Routes Copyright Kenneth M. Chipps Ph.D.
86 Populating Routing Tables Let’s now look a little closer at the details of the two ways of populating routing tablesStatic RoutesDynamic RoutesCopyright Kenneth M. Chipps Ph.D.
87 Copyright 2005-2009 Kenneth M. Chipps Ph.D. www.chipps.com Static RoutesTo use static routes an entry is made directly into the router's routing table from the command line of the router's operating systemFor example, to make such an entry into the routing table of a Cisco router the following is doneCopyright Kenneth M. Chipps Ph.D.
88 Copyright 2005-2009 Kenneth M. Chipps Ph.D. www.chipps.com Static RoutesAt the enable levelroutername#config terminalroutername(config)#ip route S0routername#CTRL ZThis is read as followsThe command is ip routeThe IP address is the address to be entered into the tableCopyright Kenneth M. Chipps Ph.D.
89 Copyright 2005-2009 Kenneth M. Chipps Ph.D. www.chipps.com Static RoutesNext is a subnet mask to identify the network portion of the IP addressLast is the address of the directly connected interface of the next hop routerIn this case out serial port 0The above is done for all routes at each routerThis method is used for two main reasonsCopyright Kenneth M. Chipps Ph.D.
90 Copyright 2005-2009 Kenneth M. Chipps Ph.D. www.chipps.com Static RoutesThe first is it is all that is needed for a private network in a hub and spoke arrangementThe second reason is securityIf no information is exchanged with any outside entity, it is less likely that anyone will be able to determine the extent and layout of your networkCopyright Kenneth M. Chipps Ph.D.
91 Copyright 2005-2009 Kenneth M. Chipps Ph.D. www.chipps.com Static Default RouteThere is a special kind of static route that is used when an entry cannot be found in the routing table for the network of interestThis special type of static route is also used on stub networks when there is no other way out of the networkIn this case every packet that does not belong on the LAN is sent out to the default routeCopyright Kenneth M. Chipps Ph.D.
92 Copyright 2005-2009 Kenneth M. Chipps Ph.D. www.chipps.com Static Default RouteWhen a router receives a packet whose network address is not found in the router’s IP routing table, the router discards the packet, unless a default route has been configuredA default route tells a router where to send packets that do not match any of that router’s other IP routesCopyright Kenneth M. Chipps Ph.D.
93 Copyright 2005-2009 Kenneth M. Chipps Ph.D. www.chipps.com Static Default RouteDefault routes can be most useful in two major casesIn routers that have only one possible physical path to forward packets to the rest of the internetworkTo route packets to the Internet, when there is a single connection to the InternetFor example in the diagram that followsCopyright Kenneth M. Chipps Ph.D.
94 Copyright 2005-2009 Kenneth M. Chipps Ph.D. www.chipps.com Static Default RouteEach branch office has one router, with the only link back to the headquartersThe enterprise network also has one link to an ISP for its Internet connectionConfiguring of static default route is similar for both casesOn branch router R1, the command would be as followsip route S0/0Copyright Kenneth M. Chipps Ph.D.
95 Copyright 2005-2009 Kenneth M. Chipps Ph.D. www.chipps.com Static Default RouteCopyright Kenneth M. Chipps Ph.D.
96 Copyright 2005-2009 Kenneth M. Chipps Ph.D. www.chipps.com Gateway of Last ResortThis type of route is also called a gateway of last resort, since without a default route, a router discards packets whose destination address does not match the router’s routing tableCopyright Kenneth M. Chipps Ph.D.
97 Floating Static Routes A floating static route is a static route that the administrator wants to be used some of the timeThe term floating comes from the idea that the static route leaves the routing table under some conditions and comes back into the routing table under other conditionsCopyright Kenneth M. Chipps Ph.D.
98 Floating Static Routes Floating static routes can be very useful for dial backup, using the following logicWhen a WAN connection is up, the router should ignore the static route and instead use the routes learned by the routing protocolThese routes will forward packets out the permanent WAN connectionWhen the permanent WAN connection is down, use the statically defined route that sends traffic over the dial backup linkCopyright Kenneth M. Chipps Ph.D.
99 Advertising Default Routes In some cases, it makes sense to distribute a default route throughout an internetworkCopyright Kenneth M. Chipps Ph.D.
100 Advertising Default Routes For example in the diagram that followsAll routers in the enterprise internetwork learn about all subnets of Class B network via RIPRouter R-core defines a static default route pointing to the InternetRouter R-core advertises a default route to the rest of the routers in the enterpriseCopyright Kenneth M. Chipps Ph.D.
101 Advertising Default Routes Copyright Kenneth M. Chipps Ph.D.
102 Copyright 2005-2009 Kenneth M. Chipps Ph.D. www.chipps.com Dynamic RoutesUnlike static routes, which point one way and only one way, a dynamic routing protocol can compensate for changes in the network without someone having to go to the command line of each router and make the changeThere are only a few major routing protocols that can do this work for youCopyright Kenneth M. Chipps Ph.D.
103 Copyright 2005-2009 Kenneth M. Chipps Ph.D. www.chipps.com Dynamic RoutesOf course all the routers must speak the same language for this to workRecall as well that dynamic routing protocols fall into two general classesDistance VectorLink StateCopyright Kenneth M. Chipps Ph.D.
105 Copyright 2005-2009 Kenneth M. Chipps Ph.D. www.chipps.com Link State ProtocolsLink state routing protocols includeOSPF – Open Shortest Path First IS-IS – Intermediate System to Intermediate SystemCopyright Kenneth M. Chipps Ph.D.
106 Copyright 2005-2009 Kenneth M. Chipps Ph.D. www.chipps.com Path Vector ProtocolsThe final type is the path vector sort, of which there is only oneBorder Gateway ProtocolCopyright Kenneth M. Chipps Ph.D.
107 Copyright 2005-2009 Kenneth M. Chipps Ph.D. www.chipps.com Which One to UseCisco will spend more time on the routing protocols they invented or preferIn the real world the two main interior routing protocols areOSPFOSPF is used by both Cisco only and mixed vendor shopsEIGRPEIGRP is used by Cisco only operationsCopyright Kenneth M. Chipps Ph.D.
108 Copyright 2005-2009 Kenneth M. Chipps Ph.D. www.chipps.com Which One to UseThere is a reasonable amount of RIP in use stillIGRP is rarely used, but is seen in small operationsIS-IS is used by some ISPs and the likeCopyright Kenneth M. Chipps Ph.D.
109 Copyright 2005-2009 Kenneth M. Chipps Ph.D. www.chipps.com ReviewWhat is the difference between static and dynamic routingWhat is the difference between distance vector and link state routing protocolsWhat dynamic routing protocols are commonly usedCopyright Kenneth M. Chipps Ph.D.
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