ccna3 – module 3 eigrp
DESCRIPTION
CCNA3 – module 3 EIGRP. EIGRP. Cisco proprietary, released in 1994 Based on IGRP EIGRP is an advanced distance-vector routing protocol that relies on features commonly associated with link-state protocols. (sometimes called a hybrid routing protocol ) Supports VLSM and CIDR - PowerPoint PPT PresentationTRANSCRIPT
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CCNA3 – module 3 EIGRPCCNA3 – module 3 EIGRP
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EIGRPEIGRP Cisco proprietary, released in 1994Cisco proprietary, released in 1994 Based on IGRPBased on IGRP EIGRP is an EIGRP is an advanced distance-vectoradvanced distance-vector
routing protocol that relies on features routing protocol that relies on features commonly associated with link-state commonly associated with link-state protocols. (sometimes called a protocols. (sometimes called a hybrid hybrid routing protocolrouting protocol))
Supports VLSM and CIDRSupports VLSM and CIDR Allows for multiple routed protocolsAllows for multiple routed protocols
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EIGRPEIGRP Uses Hello protocols to create and maintain neighbor Uses Hello protocols to create and maintain neighbor
relationships and to determine when a link is down. relationships and to determine when a link is down. (Like link-state)(Like link-state) Every 5 seconds, with a hold timer of 15 secondsEvery 5 seconds, with a hold timer of 15 seconds Links less than T1 speed, Hellos are every 60 Links less than T1 speed, Hellos are every 60
seconds, hold timer of 180 secondsseconds, hold timer of 180 seconds Partial routing updates in response to topology Partial routing updates in response to topology
changeschanges When a change in topology occurs, EIGRP does not When a change in topology occurs, EIGRP does not
flood updates like link-state protocols, but flood updates like link-state protocols, but immediatelyimmediately sends those changes to its neighbors.sends those changes to its neighbors.
Has speed and efficiency of routing updates like a Has speed and efficiency of routing updates like a link-state protocol, along with a topology database.link-state protocol, along with a topology database.
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EIGRP BenefitsEIGRP Benefits
Rapid Convergence – DUAL routing algorithm
Efficient use of bandwidth
partial, bounded updates – only sent to routers that need the information & not entire routing table
small “Hello” packets to keep in touch with other routers – minimal use of bandwidth
Supports VLSM and CIDR
Multiple network-layer support (multiprotocol)
IP, IPX, and AppleTalk
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EIGRP and IGRPEIGRP and IGRP
AutomaticallyAutomatically redistributes when using same AS redistributes when using same AS number.number.
Topology example….Topology example….
RTC
RTB
RTA
RTD
192.168.1.0/24
10.1.1.0/24
172.16.1.0/24
IGRP 2446EIGRP 2446
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Metric calculation: IGRP/EIGRPMetric calculation: IGRP/EIGRP
(with the following default constant values):(with the following default constant values):
Constant ValueConstant Value
K1K1 1 1
K2K2 0 0
K3 1K3 1
K4K4 0 0
K5K5 0 0
Notes Notes k2k2 metric effects metric effects LOADLOAD k4k4 and and k5k5 effects effects RELIABILITYRELIABILITY
metric = [K1 * bandwidth + ((K2 * bandwidth) / (256 * load)) + (K3 * delay)] * [K5/(reliability + K4)]
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Metric CalculationMetric Calculation
Simplify the previous equation by Simplify the previous equation by applying the default constants…applying the default constants…
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The metrics used by EIGRP in making routing The metrics used by EIGRP in making routing decisions are (decisions are (lower the metric the betterlower the metric the better):):
bandwidthbandwidth delaydelay loadload reliabilityreliability
By default, EIGRP uses only:By default, EIGRP uses only: Bandwidth (carrying capacity)Bandwidth (carrying capacity) Delay (end-to-end travel time)Delay (end-to-end travel time)
Metric CalculationMetric Calculation
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If these are the default:If these are the default: bandwidth (default)bandwidth (default) delay (default)delay (default)
When are these used?When are these used? loadload reliabilityreliability
Use Use show interfaceshow interface command to view the command to view the metrics used on a specific interface that is metrics used on a specific interface that is routing EIGRP. routing EIGRP.
Metric CalculationMetric Calculation
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Metric Calculation – show interfacesMetric Calculation – show interfaces
Router> show interfaces s1/0
Serial1/0 is up, line protocol is up
Hardware is QUICC Serial
Description: Out to VERIO
Internet address is 207.21.113.186/30
MTU 1500 bytes, BW 1544 Kbit, DLY 20000 usec,
rely 255/255, load 246/255
Encapsulation PPP, loopback not set
Keepalive set (10 sec)
<output omitted>
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BandwidthBandwidth Expressed in Expressed in kilobitskilobits ( (show interfaceshow interface)) This is a This is a static numberstatic number and used for metric and used for metric
calculations only.calculations only. Does not necessarily reflect the actual bandwidth of Does not necessarily reflect the actual bandwidth of
the link.the link. You can adjust the bandwidth metric on an interface You can adjust the bandwidth metric on an interface
using what command?using what command? What command restores the interface bandwidth to What command restores the interface bandwidth to
the original default?the original default?
The default values:The default values: What is the default bandwidth of serial interfaces on What is the default bandwidth of serial interfaces on
CISCO routers?CISCO routers?
Metric Calculation – BandwidthMetric Calculation – Bandwidth
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DelayDelay Like bandwidth, delay it is a Like bandwidth, delay it is a static numberstatic number.. Expressed in Expressed in microsecondsmicroseconds, , millionths of a millionths of a
secondsecond (Uses the Greek letter mu with an S, (Uses the Greek letter mu with an S, S, NOT “ms” S, NOT “ms”
which is millisecond or which is millisecond or thousandths of a secondthousandths of a second))
The default values:The default values: What is the default delay of a Cisco serial What is the default delay of a Cisco serial
interface?interface?
IGRP/EIGRP metric uses the IGRP/EIGRP metric uses the sum of all of the sum of all of the delaysdelays of all of the outbound interfaces to the of all of the outbound interfaces to the destination network.destination network.
Metric Calculation – DelayMetric Calculation – Delay
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Changing the delay informational parameter:Changing the delay informational parameter:The delay can be changed using:The delay can be changed using: Router(config-if)# Router(config-if)# delaydelay tens-of- tens-of-SS (microseconds)(microseconds) Example of changing the delay on a serial interface to Example of changing the delay on a serial interface to
30,000 microseconds30,000 microseconds:: Router(config-if)# Router(config-if)# delaydelay 3000 3000
To restore the 20,000 microsecond default value: To restore the 20,000 microsecond default value: Router(config-if)# Router(config-if)# no delayno delay
Metric Calculation – DelayMetric Calculation – Delay
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IGRP vs EIGRP Metric CalculationIGRP vs EIGRP Metric Calculation
The differenceThe difference:: IGRP metric is 24 bits longIGRP metric is 24 bits long EIGRP metric is 32 bits longEIGRP metric is 32 bits long EIGRP metric is 256 times greater for the EIGRP metric is 256 times greater for the
same routesame route EIGRP allows for finer comparison of EIGRP allows for finer comparison of
potential routespotential routes
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IGRP vs EIGRP Metric CalculationIGRP vs EIGRP Metric Calculation
IGRPIGRP bandwidth = (10,000,000 ÷ bandwidth = (10,000,000 ÷ bandwidthbandwidth)) delay = delay = delay ÷ delay ÷ 1010
EIGRPEIGRP bandwidth = (10,000,000 ÷ bandwidth = (10,000,000 ÷ bandwidthbandwidth) * 256) * 256 delay = (delay = (delay ÷ delay ÷ 10) * 256 10) * 256
Note: The reference-bandwidth Note: The reference-bandwidth
For both IGRP and EIGRP: 10For both IGRP and EIGRP: 1077, , (10,000,000/bandwidth), whereas(10,000,000/bandwidth), whereas with OSPF it with OSPF it was 10was 108 8 (100,000,000/bandwidth)(100,000,000/bandwidth)
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Metrics – HOP COUNTMetrics – HOP COUNT
EIGRP also imposes a maximum hop count EIGRP also imposes a maximum hop count of 224of 224
IGRP maximum hop count of 255IGRP maximum hop count of 255 RIP maximum hop count of 15RIP maximum hop count of 15
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EIGRP ConfigurationEIGRP Configuration
RTA(config)# RTA(config)# router eigrp router eigrp ASAS
RTA(config-router)# network network
RTA(config-router)# eigrp log-neighbor-changes
RTA(config-if)#bandwidth kilobits
AS must be the same on all routers in the AS
If AS’s are identical on a router running both IGRP and EIGRP, routing tables are redistributed automatically.
Enables logging of neighbor adjacency changes to monitor stability & help detect problems
CISCO recommends this command.
EIGRP assumes default if not set.
If the link is slower, router might not converge, routing updates may be lost, or suboptimal path selection may result.
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EIGRP tablesEIGRP tables
Neighbor Topology Routing
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EIGRP Neighbor tablesEIGRP Neighbor tables
Lists adjacent routers One table for each routed protocol that
EIGRP supports
RTX#show ip eigrp neighborsIP-EIGRP neighbors for process 1
H Address Interface Hold Uptime SRTT RTO Q Seq
(sec) (ms) Cnt Num
1 10.2.0.2 Se1 12 00:27:39 333 1998 0 10
0 10.1.0.1 Se0 14 01:17:14 40 240 0 27
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EIGRP Neighbor tablesEIGRP Neighbor tables
Fields in neighbor table: Neighbor address (Address) Hold time (Hold Uptime) Smooth round-trip timer (SRTT) Queue count (Q Cnt) Sequence number (Seq No)
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DUAL – calculating best pathsDUAL – calculating best paths
When the hold time expires, DUAL is informed of the topology change and must recalculate the new topology.
DUAL (Diffusing Update Algorithm) – allows routers involved in a topology change to synchronize at the same time, while not involving routers that are unaffected by the change (distance-vector algorithm)
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EIGRP Topology tablesEIGRP Topology tables
Contains all of the EIGRP routing tables in the autonomous system DUAL combines information supplied by
neighbor and topology tables and calculates the lowest cost routes to each destination.
EIGRP routers track changes and switch to alternate routes when necessary
DUAL places this primary route, or successor route, information in the routing table
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EIGRP Topology tablesEIGRP Topology tablesTopology tables includes: Feasible distance (FD) – lowest calculated metric to
each destination. Route source (via xxx.xxx.xxx.xxx) – ID of router that
originally advertised route Reported distance (RD) – distance that an adjacent
neighbor reports to specific destination Interface information – interface through which the
destination is reachable Route status –
passive (P) – route is stable and ready for use Active (A) – route is in the process of being recomputed by
DUAL
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EIGRP Topology tablesEIGRP Topology tables
RTX#show ip eigrp topologyIP-EIGRP Topology Table for process 100
Codes: P - Passive, A - Active, U - Update, Q - Query, R - Reply, r - Reply status
P 200.10.3.0/24, 1 successors, FD is 2169856
via Connected, Serial1
via Redistributed (2169856/0)
P 200.10.4.0/24, 1 successors, FD is 2169856
via Connected, Serial0
RD
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EIGRP Topology tablesEIGRP Topology tables
Successor – route that is selected as the primary route to use to reach a destination.
DUAL identifies and places route in routing table There can be up to four successor routes for any
particular route. Copy of successor is also placed in topology table
EIGRP sorts the topology table so that the successor routes are at the top, followed by the feasible successors. Bottom of list may include routes that DUAL believes to be loops.
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EIGRP Topology tablesEIGRP Topology tables
Feasible Successor – backup route Identified at same time as successor but kept only
in the topology table May have multiple feasible successors but not
mandatory to have any They are neighbors that are downstream (closer
to the destination) Must have lower advertised cost (RD) than
existing successor’s FD If feasible successor not identified, active status
placed on route and query packets sent to all neighbors to recompute topology.
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Successor & Feasible SuccessorSuccessor & Feasible Successor
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Recomputation of RoutesRecomputation of RoutesIf route becomes unavailable and DUAL cannot find feasible successor.
Neighbor routers are compelled to answer query for a loop-free path.
If neighbor has no route, it responds so.
Excess computation = network instability
To prevent convergence problems, DUAL always tries to find a feasible successor before resorting to recomputation
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Recomputation of RoutesRecomputation of RoutesStuck in Active routers –
one or more routers don’t respond to query (180 seconds) then routes placed in stuck in active state
EIGRP then clears its table of neighbors that did not respond
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Route TaggingRoute TaggingRouting Table –
Internal routes
routes originating within the EIGRP AS
External routes
routes originating outside the EIGRP AS
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Routing Table & TaggingRouting Table & TaggingRouterB#show ip routeCodes: C - connected, S - static, I - IGRP, R - RIP, M - mobile, B – BGP, D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area, E1 - OSPF external type 1, E2 - OSPF external type 2, E – EGP, i - IS-IS, L1 - IS-IS level-1, L2 - IS-IS level-2, * - candidate default U - per-user static route
Gateway of last resort is not set
C 10.1.1.0 is directly connected, Serial0
D 172.16.0.0 [90/2681856] via 10.1.1.0, Serial0
D EX 192.168.1.0 [170/2681856] via 10.1.1.1, 00:00:04, Serial0
External EIGRP routes are redistributed from IGRP networks
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RTA#show ip route<output omitted>C 10.1.1.0 is directly connected, Serial0D 172.16.0.0 [90/2681856] via 10.1.1.0, Serial0D EX 192.168.1.0 [170/2681856] via 10.1.1.1, 00:00:04, Serial0
External EIGRP routes are redistributed from IGRP networks
RTC#show ip route<output omitted>C 192.168.1.0 is directly connected, Serial0I 10.1.0.0 [100/10476] via 192.168.1.1, 00:00:04, Serial0I 172.16.0.0 [100/10476] via 192.168.1.1, 00:00:04, Serial0
RTC only sees IGRP routes
192.168.1.0 was redistributedfrom IGRP
RTC
RTB
RTA
RTD
192.168.1.0/24
10.1.1.0/24
172.16.1.0/24
IGRP 2446EIGRP 2446
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Hellos & RTPHellos & RTPHello Packets
Sent every 5 seconds (high-bandwidth links) and every 60 seconds by default (low-bandwidth links)As long as routers receive hello packets – route in passive state
Reliable Transport Protocol (RTP)Layer 4 protocolGuarantees delivery of packetsAllows EIGRP to multicast and unicast to different peers simultaneously
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DUAL FSMDUAL FSMDUAL Finite-State Machine (DUAL FSM)
Full name of DUAL technologyTracks routes advertised by neighbors and uses composite metric to compare themGuarantees each path is loop-freeInserts lowest-cost paths (successor routes) into routing tableNeighbor & Topology tables supply DUAL with route information to make decisions quickly
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DUAL FSMDUAL FSM
FD is not mandatory
2 < 3
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EIGRP PacketsEIGRP Packets
•Hello Packets
•5 second updates (T1/Point-to-Point link)
•Multicast on IP address 224.0.0.10
•Hold Time = 3 times the Hello interval
(15 seconds)
•Neighbor routers hello and dead intervals do not need to match with EIGRP (unlike OSPF)
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EIGRP PacketsEIGRP Packets
•Acknowledgement•Used by RTP to signal reliable exchange of information
•Hello packet without data; unicast to specific host
•Update•Discovery of new neighbor
•EIGRP router sends unicast to neighbor so that it can add to its topology table
•EIGRP router send multicast to all neighbors if topology change occurs
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EIGRP PacketsEIGRP Packets
•Query & Reply•Query - Used to obtain specific information from one or all of its neighbors (multicast or unicast)
•Reply – response to query (unicast)
•Used, for example, if DUAL places a route in active state and multicasts neighbors, searching for successor
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EIGRP Route SummarizationEIGRP Route SummarizationEIGRP automatically summarizes routes at the classful boundary
This may not be preferable, especially if using VLSM
To disable auto-summarization:
Router(config-router)#no auto-summary
Manual Summarization command:
Router(config-if)#ip summary-address eigrp AS ip-address subnet-mask administrative distance(configured on a per-interface basis)
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EIGRP Route SummarizationEIGRP Route Summarization
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Verifying EIGRPVerifying EIGRP
Show ip eigrp neighbors Show ip eigrp interfaces Show ip eigrp topology Show ip eigrp topology all-links Show ip eigrp traffic AS Debug eigrp fsm Debug eigrp packets
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RIP, IGRP, & OSPF RIP, IGRP, & OSPF TroubleshootingTroubleshooting
Show & debug commandsShow & debug commands Debug ip rip Debug ip igrp events Debug ip igrp transactions Debug ip ospf events Show ip route Show running-config Show ip protocols show ip ospf neighbor