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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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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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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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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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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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EIGRP Successor
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EIGRP Feasible Successor
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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