CCNA2_M6_Routing_and_Routing_Protocols (1130732)

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CCNA – Semester2Module 6Routing and Routing ProtocolsObjectives• Introduction to static routing• Dynamic routing overview• Routing protocols overviewIntroduction to Static RoutingIntroducing routing• Routing is the process that a router uses toforward packets toward the destination network.• A router makes decisions based upon thedestination IP address of a packet.• In order to make the correct decisions, routersmust learn the direction to remote networks.Route TypesThe Administrative Distance• AD is a rating of the trustworthiness of arouting information source, expressed as anumeric value from 0 to 255. The higher thenumber, the lower the trustworthinessrating.• Example:–––––Directed connectionStatic route (by default)IGRPOSPFRIP01100110120Static route• Advantages:– Require very little maintenance on small networks– No network overhead– May hide parts of networks• Disadvantages:– Require a tremendous amount of administrative time onlarge networks– Lack scalabilityThe IP ROUTE commandRouter (config)#ipip routeroute networknetwork [[ maskmask ]] {{ addressaddress || interfaceinterface }} [[ distancedistance ]][[ permanent]permanent ]• Defines a path to an IP destination network or subnetip route commandDescriptionnetworkdestination networkmaskdest.

network maskaddressIP address of next hopinterfaceName of interface to get to destinationdistanceAdministrative distancepermanentif set, route will not be removed when intf. isshutdownStatic route commandAD in static route• A route with a lower AD will be installed beforean identical route with a higher AD.• The default AD when using next-hop address is1, while the default AD when using the outgoinginterface is 0.• If an administrative distance other than thedefault is desired, a value between 0 and 255 isenteredRoute in Routing Table• If the router cannot reach the outgoing interfacethat is being used in the route, the route will notbe installed in the routing table.• This means if that interface is down, the routewill not be placed in the routing table• To hold the route in routing table even ifassociated outgoing interface is down, usepermenent parameter.Default Route• Default routes are used to route packets withdestinations that do not match any of the otherroutes in the routing table.• Routers are typically configured with a defaultroute for Internet-bound traffic.ip route 0.0.0.0 0.0.0.0 [next-hop-address | outgoinginterface]Using the DEFAULT IP ROUTE commandVerifying static route configuration• show running-config to verify that the static routewas entered correctly.• show ip route command to make sure that thestatic route is present in the routing table.Troubleshooting static route configuration• Show ip route command• Ping command• Traceroute commandDynamic Routing OverviewRouted Protocol• A routed protocol is used to direct user traffic.• A routed protocol provides enough informationin its network layer address to allow a packet tobe forwarded from one host to another based onthe addressing scheme.• Examples of routed protocols are:– Internet Protocol (IP)– Internetwork Packet Exchange (IPX)Routing Protocol• A routing protocol is the communication used betweenrouters.• A routing protocol allows one router to shareinformation with other routers regarding the networks itknows about.• Examples of routing protocols are:––––Routing Information Protocol (RIP)Interior Gateway Routing Protocol (IGRP)Enhanced Interior Gateway Routing Protocol (EIGRP)Open Shortest Path First (OSPF)Autonomous systems•••An autonomous system (AS) is a collection of networks under acommon administration sharing a common routing strategy.The American Registry of Internet Numbers (ARIN), a serviceprovider, or an administrator assigns an identifying number to eachAS.This autonomous system number is a 16 bit number.Purpose of a routing protocol• The goal of a routing protocol is to build andmaintain the routing table.• This table contains the learned networks andassociated ports for those networks.Updating route• The routing protocol learns all available routes, placesthe best routes into the routing table, and removesroutes when they are no longer valid.• The network knowledgebase needs to reflect anaccurate consistent view of the current topology.Convergence• When all routers in an internetwork are operating withthe same routing knowledge, the internetwork is said tohave converged.• During convergence, problems may occur like: routingloops, inconsistent traffic forwarding, inconsistentrouting table entries.• Fast convergence is desirable because it reduces theperiod of time in which routers would continue to makeincorrect routing decisions.Classes of routing protocols• Most routing algorithms can be classified into one oftwo categories:– distance vector– link-stateDistance vector algorithm• Pass periodic routing update (copies of arouting table) from router to router.• These regular updates between routerscommunicate topology changes.• Each router receives a routing table from itsdirectly connected neighbors.• Distance-vector algorithms do not allow arouter to know the exact topology of aninternetwork.Distance Vector DiscoveryLink-State Routing• Also known as Dijkstras algorithm or as SPF(shortest path first) algorithms.• Link-state routing algorithms maintain acomplex database of topology information• A link-state routing algorithm maintains fullknowledge of distant routers and how theyinterconnect.Link-State ConceptsLink-State ConcernsDistance Vector vs.

Link StateRouting Protocols OverviewRouter Functions• A router has two basic functions:– Path determination occurs at the network layer, enables arouter to evaluate the paths to a destination– Switching function is the internal process used by a routerto accept a packet on one interface and forward it to asecond interface on the same router.Communicate Path InformationAddressing: Network and Host••Network address: Used to determine path to a networkHost address: Specifies specific port or device on a networkHow distances are determined• Primary objective of routing protocol is todetermine the best route to put in therouting table.• Each routing algorithm interprets what isbest in its own way.• Routing algorithm generates a number,called the metric value, for each paththrough the network.• Typically, the smaller the metric number, thebetter the path.Distance in MetricsThe router and network CommandsIP Routing Configuration TasksRouting protocolsRouting Information Protocol (RIP)• It is a distance vector routing protocol.• Hop count is used as the metric for pathselection.• If the hop count is greater than 15, the packet isdiscarded.• Routing updates are broadcast every 30seconds, by default.Interior Gateway Routing Protocol (IGRP)• Cisco proprietary protocol• It is a distance vector routing protocol.• Bandwidth, load, delay and reliability are usedto create a composite metric.• Routing updates are broadcast every 90seconds, by default.Open Shortest Path First (OSPF)• It is a link-state routing protocol.• Open standard routing protocol described inRFC 2328.• Uses the SPF algorithm to calculate the lowestcost to a destination.• Routing updates are flooded as topologychanges occur.Enhanced-IGRP (EIGRP)••••Cisco proprietary protocolIt is an enhanced distance vector routing protocol.Uses load balancing.Uses a combination of distance vector and link-statefeatures.• Uses Diffused Update Algorithm (DUAL) to calculate theshortest path.• Routing updates are broadcast every 90 seconds or astriggered by topology changes.Border Gateway Protocol (BGP)••••Exterior routing protocol.It is a distance vector exterior routing protocol.Used between ISPs or ISPs and clients.Used to route Internet traffic betweenautonomous systems.Summary• Configure static route, default route, float staticroute• Protocol administrative distance• Routed and routing protocol• Distance vector and link state routing protocol• Router functions• Routing protocols metrics• IP routing configuration tasksLab TopologyF0/0F0/0S0/0S0/1Lab_ELab_BS0/1S0/0S0/1S0/1S0/1Lab_CLab_AS0/0S0/0F0/0F0/0S0/1Lab_FLab_DF0/0F0/0PortLab_ALab_BLab_CLab_DLab_ELab_FS0/0N/A199.6.13.1/24204.204.7.1/24142.18.0.1/1634.10.120.1/16N/AS0/1201.10.11.1/24201.10.11.2/24199.6.13.2/24204.204.7.2/24142.18.0.2/1634.10.210.5/16F0/0172.16.11.1/2410.0.0.1/8172.16.11.2/24192.168.1.1/2410.0.0.2/8192.168.1.2/24CCNA2 – Module6.

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