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    1

    CCNA Semester 3

    Chapter 03Chap

    ter 03

    EIGRPEIGRP

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    ObjectivesObjectives

    Describe the differences between EIGRP andIGRP

    Describe the key concepts, technologies, anddata structures of EIGRP

    Understand EIGRP convergence and the basicoperation of the Diffusing Update Algorithm(DUAL)

    Perform a basic EIGRP configuration Configure EIGRP route summarization

    Describe the processes used by EIGRP to buildand maintain routing tables

    Verify EIGRP operations

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    3

    ObjectivesObjectives

    Describe the eight-step process for generaltroubleshooting

    Apply a logical process to routingtroubleshooting

    Troubleshoot a RIP routing process using showand debug commands

    Troubleshoot an IGRP routing process using

    show and debug commandsTroubleshoot an EIGRP routing process using

    show and debug commands

    Troubleshoot an OSPF routing process usingshow and debug commands

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    Table of ContentTable of Content

    1 EIGRP Concepts2 EIGRP Configuration

    3 Troubleshooting Routing Protocols

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    5

    EIGRP CONCEPTSEIGRP CONCEPTS

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    EIGRP OverviewEIGRP Overview

    Cisco released EIGRP in 1994 as a scalable,improved version of its proprietary distancevector routing protocol, IGRP.

    Unlike IGRP, which is a classful routing protocol,EIGRP supports CIDR and VLSM.

    Hybrid routing protocol

    Fast convergence times

    Multiple network-layer protocols supported

    Reduced bandwidth usage

    Easy to configure

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    EIGRP and IGRP compatibilityEIGRP and IGRP compatibility

    Default: k1 = 1, k2 = 0, k3 = 1, k4 = 0, k5 = 0.

    Metric = Bandwidth + Delay

    EIGRP scales IGRP's metric by a factor of256.Because EIGRP uses a metric that is 32 bits long(IGRP 24-bit):

    Bandwidth for IGRP = (10.000.000 / bandwidth)

    Bandwidth for EIGRP = (10.000.000 / bandwidth)*256 Delay for IGRP = (delay/10)

    Delay for EIGRP = (delay/10) * 256

    k1xBW +k2xBW

    256 Load+ k3xDelayMetric =

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    EIGRP and IGRP compatibilityEIGRP and IGRP compatibility

    192.168.1.0/24

    RTC

    EIGRP 2446IGRP 2446

    172.16.1.0/24

    10.1.1.0/24

    EIGRP and IGRP automatically redistributeroutes between autonomous systems withsame autonomous system (AS) number.

    IGRP has a maximum hop count of 255.

    EIGRP has a maximum hop count limit of224.

    RTD

    RTA

    RTB

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    Neighbor TableAppleTalkDestination Next Hop

    Router

    Neighbor TableIPXDestination Next Hop

    Router

    Neighbor TableIPNext-Hop InterfaceRouter

    EIGRP concepts and terminology

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    Neighbor TableAppleTalkDestination Next Hop

    Router

    Neighbor TableIPXDestination Next Hop

    Router

    Neighbor TableIPNext-Hop InterfaceRouter

    Topology TableAppleTalkDestination 1 Next Router 1/CostDestination 1 Next Router 1/Cost

    Topology TableIPXDestination 1 Next Router 1/CostDestination 1 Next Router 1/Cost

    Topology TableIPDestination 1

    EIGRP concepts and terminology

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    Topology TableAppleTalkDestination 1 Next Router 1/CostDestination 1 Next Router 1/Cost

    Topology TableIPXDestination 1 Next Router 1/CostDestination 1 Next Router 1/Cost

    Topology TableIPDestination 1

    Routing TableAppleTalkDestination 1 Next Router XDestination 1 Next Router X

    Routing TableIPXDestination 1 Next Router XDestination 1 Next Router X

    Routing TableIPDestination 1

    Neighbor TableAppleTalkDestination Next Hop

    Router

    Neighbor TableIPXDestination Next Hop

    Router

    Neighbor TableIPNext-Hop InterfaceRouter

    EIGRP concepts and terminology

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    Topology TableAppleTalkDestination 1 Next Router 1/CostDestination 1 Next Router 1/Cost

    Topology TableIPXDestination 1 Next Router 1/CostDestination 1 Next Router 1/Cost

    Topology TableIPDestination 1 Successor

    Routing TableAppleTalkDestination 1 Next Router XDestination 1 Next Router X

    Routing TableIPXDestination 1 Next Router XDestination 1 Next Router X

    Routing TableIPDestination 1 Successor

    Neighbor TableAppleTalkDestination Next Hop

    Router

    Neighbor TableIPXDestination Next Hop

    Router

    Neighbor TableIPNext-Hop InterfaceRouter

    EIGRP concepts and terminology

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    Topology TableAppleTalkDestination 1 Next Router 1/CostDestination 1 Next Router 1/Cost

    Topology TableIPXDestination 1 Next Router 1/CostDestination 1 Next Router 1/Cost

    Topology TableIPDestination 1 SuccessorDestination 1 Feasible Successor

    Routing TableAppleTalkDestination 1 Next Router XDestination 1 Next Router X

    Routing TableIPXDestination 1 Next Router XDestination 1 Next Router X

    Routing TableIPDestination 1 Successor

    Neighbor TableAppleTalkDestination Next Hop

    Router

    Neighbor TableIPXDestination Next Hop

    Router

    Neighbor TableIPNext-Hop InterfaceRouter

    EIGRP concepts and terminologyEIGRP concepts and terminology

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    Network Z

    EIGRP Successors and Feasible successor

    RTA

    RTB

    I have a routeto Z, with ametric of 5

    RTB is successor to NetZ

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    Network Z

    EIGRP Successors and Feasible successor

    RTA

    RTB

    RTC

    I have aroute to Z,

    with a metricof 5

    I have a routeto Z, with ametric of 5

    RTB is successor to NetZRTB is successor to NetZ

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    Network Z

    EIGRP Successors and Feasible successor

    RTA

    RTX

    RTB

    RTC

    RTY

    I have aroute to Z,

    with a metricof 5

    I have a routeto Z, with ametric of 6

    I have a routeto Z, with ametric of 5

    RTB is successor to NetZRTB is successor to NetZRTX is feasiblesuccessor to Net Z

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    EIGRP designEIGRP design

    EIGRP's advantages over simple distance-vector protocols :

    Rapid convergence (because of useDiffusing Update Algorithm - DUAL)

    Efficient use of bandwidth

    Partial, bounded (incremental) updates

    Minimal consumption of bandwidth when

    the network is stable with small hellopackets

    Support for VLSM and CIDR

    Multiple network-layer support and

    Independence from routed protocols

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    EIGRP technologiesEIGRP technologies

    Many new technologies are improvement inoperating efficiency, speed of convergence,or functionality relative to others routing

    protocols.

    Four categories:

    Neighbor discovery and recovery

    Reliable Transport Protocol (RTP)

    DUAL finite-state machine algorithm

    Protocol-dependent modules (PDM)

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    Neighbor discovery and recoveryNeighbor discovery and recovery

    EIGRP routers establish adjacencies with neighborrouters by using small hello packets

    On IP networks, EIGRP routers send hellos to themulticast IP address 224.0.0.10

    RTA#show ip eigrp neighbors

    IP-EIGRP neighbors for process 400

    H Address Interface Hold Uptime SRTT RTO Q Seq

    (sec) (ms) Cnt Num

    1 172.68.2.2 To0 13 02:15:30 8 200 0 9

    0 172.68.16.2 Se1 10 02:38:29 29 200 0 6

    13 02:15:30

    10 02:38:29

    Bandwidth Example link Default hellointerval

    Default hold times

    T1 or less Multipoint framerelay, ISDN

    60 seconds 180 seconds

    Greater than T1 Ethernet, T1 5 seconds 15 seconds

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    Neighbor discovery and recoveryNeighbor discovery and recovery

    By forming adjacencies, EIGRP routers do:

    Dynamically learn of new routes that jointheir network

    Identify routers that become eitherunreachable or inoperable

    Rediscover routers that had previouslybeen unreachable

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    2

    I am router A, who is on the link?Hello

    A B

    1

    Initial Route DiscoveryInitial Route Discovery

    Here is my complete routing information. Update2

    Thanks for theinformation!

    Ack3Topology

    Table

    4

    Here is my complete route information.Update5

    Converged

    Thanks for the information! 6

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    2

    Reliable Transport Protocol (RTP)Reliable Transport Protocol (RTP)

    EIGRP uses RTP as its own proprietary transport-layer protocol, that can guarantee ordereddelivery of routing information to all neighbors.

    EIGRP can call on RTP to provide reliable orunreliable service as the situation warrants.

    Reliable delivery of other routing information canactually speed convergence, because EIGRP

    routers are not waiting for a timer to expirebefore they retransmit.

    With RTP, EIGRP can multicast and unicast todifferent peers simultaneously, which allows for

    maximum efficiency.

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    Reliable Transport Protocol (RTP)Reliable Transport Protocol (RTP)

    EIGRP reliable packets are packets thatrequires explicit acknowledgement:

    Update: Send routing updates

    Query: Ask neighbors about routinginformation

    Reply: Response to query about routinginformation

    EIGRP unreliable packets are packets that donot require explicit acknowledgement:

    Hello: Establish neighbor relationships

    ACK: Acknowledgement of a reliable packet

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    Diffusing Update Algorithm (DUAL) is EIGRP'sroute-calculation engine.

    Finite-state machine

    Tracks all routes advertised by neighbors

    Select loop-free path using a successor andremember any feasible successors

    If successor lost, use feasible successor

    If no feasible successor, query neighborsand recomputed new successor

    DUAL finite-state machine algorithmDUAL finite-state machine algorithm

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    DUAL DUAL Discovery routeDiscovery route

    A B

    CRouter B information

    Neighbor TableIP

    Router C information

    Router B information

    Topology TableIP

    Router C information

    Successor (primaryroute)

    Feasible successor

    Routing TableIP

    Successor (primary route)

    DUAL?

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    2

    EIGRP Successor

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    EIGRP Feasible Successor

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    2

    Feasible Successor Route

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    No EIGRP Feasible Successor

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    DUAL Example (Start)

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    DUAL Example: Link Goes Down

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    DUAL Example: D Sends Queries

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    DUAL Example: E Sends Queries

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    DUAL Example: C Replies

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    DUAL Example: E Replies

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    DUAL Example: Convergence

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    Protocol-dependent modules (PDM)Protocol-dependent modules (PDM)

    Support for routed protocols, such as IP, IPX, andAppleTalk, is included in EIGRP through PDMs.

    Easily adapt to new or revised routed protocols, suchas IPv6, by adding protocol-dependent modules.

    Each PDM is responsible for all functions related to its

    specific routed protocol. The IP-EIGRP module isresponsible for the following:

    Sending and receiving EIGRP packets that bear IPdata

    Notifying DUAL of new IP routing information that isreceived

    Maintaining the results of DUAL routing decisions inthe IP routing table

    Redistributing routing information that was learnedby other IP-capable routing protocols

    Router

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    XX

    RepliesReplies

    Router

    A

    Router

    B

    Router

    CRouter

    D

    QueriesQueries

    XX

    XX

    XX

    XX

    s In some cases, it can take too long for the query to be answered.

    s When this happens, the router that issued the query gives up and resets its

    neighbor relationship with the router that didnt answer.

    s The most basic situation where this occurs is when it simply takes too long

    for a query to reach the other end of the network and a reply to travel back.

    Stuck in Active (SIA)Stuck in Active (SIA)

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    Typically, SIAs results when a router cannotanswer a query because:

    the router is too busy to answer the query(generally high cpu utilization)

    the router cannot allocate the memory to processthe query or build the reply packet

    the circuit between the two routers is not good

    (packet loss) unidirectional links (a link on which traffic can

    only flow in one direction due to a failure)

    Stuck in Active (SIA)Stuck in Active (SIA)

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    CONFIGURING EIGRPCONFIGURING EIGRP

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    For IP networksFor IP networks

    1.router(config)# router eigrpautonomous-system-number

    AS much match all router inside AS

    1.router(config-router)# networknetwork-number

    Network number only for connected network

    1.router(config-if)# bandwidthkilobits

    Serial interface link use (if not Router take default)

    router(config-if)# eigrp log-neighbor-changes

    Enables the logging of neighbor adjacency changes

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    For IP networksFor IP networks

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    EIGRP summarization EIGRP summarization AutomaticAutomatic

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    Manual summarization

    Configurable on a per-interface basis in anyrouter within network

    When summarization is configured on aninterface, the router immediate creates a routepointing to null zero

    Loop prevention mechanism

    When the last specific route of the summarygoes away, the summary is deleted

    The minimum metric of the specific routes is

    used as the metric of the summary route

    EIGRP SummarizationEIGRP SummarizationManualManual

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    (config-router)#

    no auto-summary

    Turns off autosummarization for theEIGRP process

    (config-if)#

    ip summary-address eigrp

    Creates a summary address to be generated

    by this interface

    EIGRP SummarizationEIGRP SummarizationManualManual

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    Summarizing EIGRP routes Summarizing EIGRP routes ManualManual

    TC(config)#router eigrp 2446TC(config-router)#no auto-summaryTC(config-router)#exitTC(config)#interface serial0

    TC(config-if)#ip summary-address eigrp 2446 2.1.0.0 255.255.

    TC(config)#router eigrp 2446TC(config-router)#no auto-summaryTC(config-router)#exitTC(config)#interface serial0

    TC(config-if)#ip summary-address eigrp 2446 2.1.0.0 255.255.

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    Verify EIGRP withVerify EIGRP withShowShowcommandcommand

    Command Description

    Show ip eigrp neighbors[int type] [details]

    Display EIGRP neighbor table

    Show ip eigrp interfaces

    [int type] [as-number]

    [details]

    Displays EIGRP statistics and status information

    Show ip eigrp topology [as-

    number][ [ip-add] mask ]

    Display the EIGRP topology table, use the show ipeigrp topology EXEC command. Also used todetermine DUAL states & debug possible DUALproblems.

    Show ip eigrp topology

    [active | pending | zero-successor]

    Depending on keywork is used. Display all routes in

    the topology table that are either active, pending orwithout successor

    Show ip eigrp all-links Display all routes not just FC in EIGRP topology

    Show ip eigrp traffic [as-

    number]

    Display the number of EIGRP packets send and

    received.

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    Verify EIGRP withVerify EIGRP withDebugDebugcommandcommand

    Command Description

    Debug eigrp fsm This command helps you observe EIGRP FS activutyand to determine whether route updates are beinginstalled and deleted by the routing process

    debug eigrp packet Displays all types of EIGRP packets, both sent andreceived

    debug eigrp neighbor Displays the EIGRP neighbor interaction

    debug ip eigrp route Displays advertisements and changes EIGRP makes tothe routing table

    debug ip eigrp summary Displays a brief report of the EIGRP routing activity

    show ip eigrp events Displays the different categories of EIGRP activity,including route calculations

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    TROUBLESHOOTINGTROUBLESHOOTINGROUTING PROTOCOLSROUTING PROTOCOLS

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    Routing protocol troubleshooting processRouting protocol troubleshooting process

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    Routing protocol troubleshooting process (cont.)Routing protocol troubleshooting process (cont.)

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    Troubleshooting Tools and UtilitiesTroubleshooting Tools and Utilities

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    Troubleshooting RIP configurationTroubleshooting RIP configuration

    If the RIP routes are not being advertised, checkthe following:

    Layer 1 or Layer 2 connectivity issues exist.

    VLSM subnetting is configured. VLSMsubnetting cannot be used with RIP v1.

    Mismatched RIP v1 and RIP v2 routingconfigurations exist.

    Network statements are missing or incorrectlyassigned.

    The outgoing interface is down.

    The advertised network interface is down.

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    UseUse show ip protocolsshow ip protocols commandcommand

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    UseUse debug ip ripdebug ip rip commandcommand

    3d08h: RIP: bad version 128 from 160.89.80.43

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    Troubleshooting IGRP configurationTroubleshooting IGRP configuration

    If IGRP does not appear to be workingcorrectly, check the following:

    Layer 1 or Layer 2 connectivity issuesexist.

    Autonomous system numbers on IGRProuters are mismatched.

    Network statements are missing or

    incorrectly assigned.The outgoing interface is down.

    The advertised network interface isdown.

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    Troubleshooting IGRP configuration (cont.)Troubleshooting IGRP configuration (cont.)

    To view IGRP debugging information, use thefollowing commands:

    debug ip igrp transactions [host ip

    address] to view IGRP transactioninformation

    debug ip igrp events [host ipaddress] to view routing updateinformation

    To turn off debugging, use the no debug ipigrp command.

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    Troubleshooting EIGRP configurationTroubleshooting EIGRP configuration

    Some possible reasons why EIGRP may not beworking correctly are:

    Layer 1 or Layer 2 connectivity issues exist.

    Autonomous system numbers on EIGRP routers

    are mismatched. The link may be congested or down.

    The outgoing interface is down.

    The advertised network interface is down. Auto-summarization is enabled on routers with

    discontiguous subnets.

    Use no auto-summary to disable automatic

    network summarization.

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    UseUse show ip eigrp neighborsshow ip eigrp neighbors commandcommand

    One of the most common reasons for amissing neighbor is a failure on the actuallink. Another possible cause of missingneighbors is an expired holddown timer.

    RTA#show ip eigrp neighbors

    IP-EIGRP neighbors for process 400

    H Address Interface Hold Uptime SRTT RTO Q Seq

    (sec) (ms) Cnt Num

    1 172.68.2.2 To0 13 02:15:30 8 200 0 9

    0 172.68.16.2 Se1 10 02:38:29 29 200 0 613

    10

    should normallybe a value

    between 10 and

    15.

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    Troubleshooting OSPF configurationTroubleshooting OSPF configuration

    The majority of problems encountered with OSPFrelate to the formation of adjacencies and thesynchronization of the link-state databases.

    The show ip ospf neighbor command is useful

    for troubleshooting adjacency formation. Use the debug ip ospf events privileged EXEC

    command to display the following informationabout OSPF-related events:

    Adjacencies Flooding information

    Designated router selection

    Shortest path first (SPF) calculation

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    SummarySummary

    Cisco released EIGRP in 1994 as a scalable,

    improved version of its proprietary distancevector routing protocol, IGRP.

    EIGRP improves the convergence properties and

    the operating efficiency significantly over IGRP. EIGRP includes may new technologies. These

    technologies fall into one of the following fourecategories:

    Neighbor discovery and recovery

    Reliable Transport Protocol

    DUAL finite-state machine algorithm

    Protocol-dependent modules

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    Q&AQ&A