Mod 3 - EIGRP - Webiste
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Transcript of Mod 3 - EIGRP - Webiste
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Table of Contents
Basics of EIGRP
EIGRP Configuration
Monitoring EIGRP
Chapter 6 Lab Notes
EIGRP Terminology
EIGRP Operation
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Basics of EIGRP
Table of Contents
End Slide Show
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EIGRP OverviewEnhanced version of Ciscos proprietary IGRP dramatically
increases operational efficiency because EIGRP Uses a more granular version of IGRPs metrics (32 bits v. 24 bits)
Has faster convergence than any other IGP
Is scalable because of VLSM and route summarization
Supports multiple routed protocols through protocol-dependantmodules
Replaces Novell RIP and Apples RTMP
Is technically an advance distance-vector routing protocol
Uses partial updates
Hello packets for neighbor discovery
Is relatively easy to administer
However, does not have OSPFs hierarchical design (no areas)
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EIGRP Metrics
EIGRP scales IGRPs metrics by a factor of 256
IGRP metric = 24 bits; EIGRP metric = 32 bits
Bandwidth and Delay are equally weighted
Reliability, Load, and MTU are off by default
Hop count limited to 224 (IGRPs limit is 255)To remember the metric components
Big = Bandwidth
Dogs = Delay
Really = Reliability
Like = Load
Me = MTU
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EIGRP Tables
Like OSPF, EIGRP maintains three unique tables toassist in routing traffic.
Neighbor Table
Topology Table
Routing TableEIGRP maintains one table of each for each routedprotocol configured on the router.
For example, if a router was configured with IP, IPX and
AppleTalk, EIGRP would maintain3 Neighbor Tables
3 Topology Tables
3 Routing Tables
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Neighbor TableUse the show ip eigrp neighbors command
to view the table. Similar to OSPFs Adjacencies database;
Contains a list of all neighbors discovered through hellos
Maintains hello and holdtime intervals on each neighbor
Maintains information required by RTP (discussed later)
SRTTSmooth Round-trip Timer; avg. time it takes to sendand then receive a reply from that neighbor
RTORetransmission Timeout; how long to wait withoutreceiving an acknowledgement to a reliably sent packet
Router#show ip eigrp neighbors
IP-EIGRP neighbors for process 100
H Address Interface Hold Uptime SRTT RTO Q Seq
(sec) (ms) Cnt Num
0 192.168.224.2 Se0 13 00:01:28 930 5000 0 30
1 192.168.208.2 Se1 11 00:02:20 35 1140 0 21
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Topology TableUse the show ip eigrp topology [all-links]
command to view the table. Similar to OSPFs Link-State (Topology) database; Contains all routes the router has learned about from its neighbors and
all the information necessary to calculate a set of distances andvectors to all reachable destinations
FDFeasible Distance; lowest calculated metric to reach a destinationas opposed to
RDReported Distance or Advertised Distance; distance to thedestination reported by the neighbor.
Router#show ip eigrp topology
IP-EIGRP Topology Table for process 100
Codes: PPassive, A
Active, U
Update, Q
Query, R
Reply,
r Reply status
P 192.150.42.120 255.255.255.248, 1 successors, FD is 2172416
via 192.150.42.9 (2172416/2169856), Fddi0
P 192.150.42.8 255.255.255.248, 1 successors, FD is 28160
via Connected, Fddi0
Feasible Distance
Reported Distance
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Routing Table
Use the show ip route command to view table
Like all routing protocols, EIGRP maintains arouting table with
Best routes to destination networks
Maintains up to four equal-cost routes for eachdestinationUnequal-cost routes can be installed if the variance
command has been configured
You are already familiar with the routing table. You willnotice that EIGRP routes are designated with a D.
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EIGRP Terminology
Table of Contents
End Slide Show
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EIGRP Concepts & TerminologySuccessor
The best, least cost route to the destination installed in the routingtable; multiple successors can be installed for load balancing
Feasible Successor
A next-hop alternative route to the destination kept in the topology
table, ready to be installed if the successor fails; feasiblesuccessors are only in the topology table
Active State
During route recomputation, routes lost due to a successors failureare said to be in the active state. The active state ends when the
route is restored or removed.
Passive State
Installed routes that are not in the process of being recomputedare said to be in the passive state.
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EIGRP Concepts & TerminologyDiffusing Update Algorithm (DUAL)
EIGRPs route computation engine; guarantees a loop-freetopology; calculates EIGRPs metric and installs successors in therouting table & feasible successors in the topology table
Route Evaluation Occurs when the topology changes; DUAL evaluates the topology
table, searching for feasible successors and immediately installingthem, if found; no recomputation is necessary
Route Recomputation DUAL begins recomputing if no feasible successors are found;
queries neighbors for alternative routes; process ends when all
neighbors have replied and DUAL either installs successor orremoves route from the topology and routing tables.
Protocol Dependant Modules (PDM) EIGRPs scalable and adaptable feature because of its modularity;
theoretically, EIGRP does not have to be completely rewritten to
route IPv6just add a PDM.
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EIGRP Packet TypesHello Packets
Unreliable multicast to 224.0.0.10 to discover and maintainneighbors; contains the routers neighbor table Default hello interval depends on the bandwidth
1.544 Mbps = 60 sec. hello interval (180 holdtime)> 1.544 Mbps = 5 sec. hello interval (15 holdtime)
Update Packets Sent reliably, there are 2 types
Unicast to new neighbor discover; contains routing tableMulticast to all neighbors when topology changes
Query & Reply Packets Queries are multicast reliably during route recomputation, querying
neighbors for a new successor to a lost route Neighbors unicast a reply to the query whether or not they have a
route.
Acknowledgement Packets Dataless packet that acknowledges the receipt of a packet sent
reliably
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Reliable Transport Protocol
RTP is EIGRPs flexible protocol used to transportmessage types through a network
Since EIGRP is protocol independent, it has to have itsown connection-oriented and connectionless services
RTP allows unicasting and multicasting reliable andunreliable packets to peers simultaneously
RTP maintains a transmission list in the neighbor tablewith sequence numbers to determine when a requiredacknowledgement has been received.
Works much like TCPs Positive Acknowledgement withRetransmission
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EIGRP Operation
Table of Contents
End Slide Show
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EIGRP operation is completed in five stages:
Building neighbor relationships
Discovering routes
Choosing the best routes
Maintaining routes Removing routes
These stages do not necessarily occur sequentially
Building relationships and discovering routes occur
together as do choosing and maintaining routers
Note: The following EIGRP Operation discussion is adapted from CCNP
Routing Exam Prep: Exam 640-503 ( 2000)by Robert Larson, et al.
The EIGRP Process
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Building Neighbor Relationships
Neighbor relationships are established through the
use of Hello packets
A new router configured with EIGRP will multicast hellopackets to directly connected routers
The receiving routers will reply if the new router is
Configured with EIGRP
In same AS
Using the same metric weights
EIGRP routers, unlike OSPF, do not have to have the
same hello intervalsDefaults, however, are 5 sec. for > T1 and 60 sec. for T1.
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Discovering Routes
While neighbor relationships are established, the
following steps occur: The new router multicast hellos to 224.0.0.10
Directly connected routers respond with a unicastupdate packet containing all the routes in their routing
table The new router replies to all neighbors with a unicastAck packet and places the contents of the updates in itstopology table
The new router then unicast update packets to allneighbors with the contents of its topology table (this ishow its neighbors learn about the routers uniquelyconfigured networks such as a new LAN)
Neighbors reply to the new routers update with an Ack
packet.
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Building/Discovering Example
1. C comes online and multicastshellos to A & B.
2. A & B unicast an update packetcontaining routing table contents
3. C replies to unicast updates withAck packet and builds topologytable
4. C unicasts updates to A & B with
contents of topology table(includes Cs new LAN)
5. A & B reply with an Ack packet.
A B
C
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Choosing the Best Routes
After a new router has received all the updates
from directly connected neighbors, it can calculateits DUAL. First, the metric for each route in the topology table is
calculated using the following formula:
Metric = 256[(10,000,000/min. bandwidth) + sum of delays] Then, the route with the lowest cost is designated the
successor and is installed (up to 4 with equal costs) inthe routing table.
DUAL then looks for feasible successors. A feasiblesuccessor must have a lower feasible distance to thedestination than the installed routes feasible distance.
All feasible successors are maintained in the topologytable so DUAL can install them immediately if the
successor fails.
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Maintaining Routes
As new routers come online and old routes fail,
EIGRP quickly and efficiently handles thesesituations with little or no downtime.
As new routers come online, their hello packets and theensuing update process has a domino effect on thenetwork.
All routers in the AS almost instantaneously convergeon the routers new networks.
Maintaining routes also means informing directlyconnected neighbors when another neighbor stopssending hello packets at the required interval.
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Removing RoutesWhen a route fails (a directly connected neighbor is no
longer sending hellos), the detecting routers DUAL Enters the route evaluation phase.
Is there a feasible successor in the topology table? If so, immediatelyinstall it, begin routing to the alternative path, and update neighborsabout the alternative.
If no feasible successor exists, enter route recomputation
If necessary, enter the route recomputation phase.
Query neighbors for a alternative route
If neighbor has a feasible successor, it will send it to the router
If it does not have one, it will query all its directly connected neighbors,
thus flooding the AS with the query until an alternate route is or is notfound.
Once the router has received replies from all queried neighbors, it canthen recalculate the best route.
If a new alternative is found, it will be installed in the routing table.
If no new alternative is found, the old route is removed.
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EIGRP Convergence Summary1. Router detects link failure; enters route evaluation
Feasible successors are promoted to successors
Successors are installed in the routing table immediately
All neighbors are updated about the new alternate route
2. If no feasible successors, router enters route recomputation Queries are flooded throughout the AS in search of an alternate
All routers reply whether they have an alternative or not
Originating router waits for all replies before either Removing the queried network for its topology and routing tables or
Adding an alternative path for the queried network in its tables
If a query receives no response, the route becomes stuck-in-active
3. The router has now converged and will now work to converge the entire
internetwork by Generating an update and multicasting it out all interfaces
Update contains info. on what paths the router has added/removed from itstopology and routing tables
Each receiving router will replay with an Ack packet and modify tablesaccordingly
The EIGRP internetwork has now converged.
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EIGRP Configuration
Table of Contents
End Slide Show
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Similar to IGRP, EIGRP is started with the following
commands:Router(config)#router eigrp [AS_number]
Router(config-router)#network network-number
A router running both IGRP and EIGRP with the same AS numberwill automatically redistribute from one routing process into the
other EIGRP routes redistributed into IGRP are denoted with an I in therouting table.
IGRP routes redistributed into EIGRP are denoted with an D EX inthe routing table.
For interfaces whose actual bandwidth is different than
EIGRPs defaults, use the following command.Router(config-if)#bandwidth kilobits
For example, a serial link defaults to T1 speeds or 1544 kbps. Ifthe contracted speed is a T1 or 768 kbps
Router(config-if)#bandwidth 768
Basic Configuration
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Route SummarizationEIGRP recognizes two types of summary routing:
Automatic route summarization Manual route summarization
Automatic Summarization (on by default in EIGRP) Works the same as IGRP and RIP
Summarizes routes on the classful boundary; does not advertise
subnets; subnets must be contiguous. For example;
Subnets 172.16.16.0/20, 172.16.32.0/20, and 172.16.48.0/20 would beautomatically summarized as 172.16.0.0/16
Automatic summarization has its benefits Conserves resources across classful boundaries in networks with proper IP
addressing design.
Manual Summarization EIGRP can summarize routes at classless boundaries on any router
interface on the network This capability is an advantage over OSPF, which can only summarize
on ABRs and ASBRs
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Manual Summarization
Automatic summarization must be turned off.
in the routing process for EIGRP
Router(config-router)#no auto-summary
To configure a classless summary route
Subnets must be contiguous!! Use the following command on the interface that will
advertise the summary:Router(config-if)#ip summary-address eigrpAS-number ip-address mask
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Manual Summarization Example
On Router B, you would summarize routes
advertised to A as follows:!Start the routing process & disable automatic summarization
RTB(config)#router eigrp 100
RTB(config-router)#network 190.1.1.0
RTB(config-router)#network 190.1.2.0
RTB(config-router)#network 190.1.3.0
RTB(config-router)#no auto-summary
!Then on the interface, summarize the subnets advertised to A
RTB(config-router)#interface e0
RTB(config-if)#ip address 10.2.50.1 255.255.255.0
RTB(config-if)#ip summary-address eigrp 100 190.1.0.0 255.255.252.0
BA C
D
e0
e1
e2
190.1.1.0/24
190.1.3.0/24
190.1.2.0/24
10.2.10.0/24
10.2.50.0/24
190.1.0.0/22
Advertised to A
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Null0 means theres
no specific interfacefor 190.1.1.0/22; more
specific routes exist.
Manual Summarization Example
Router Bs topology table would show all the
specific routes as well as the summary:RTB#show ip eigrp topologyIP-EIGRP Topology Table for process 1
(output omitted)
P 190.1.1.0/24, 1 successors, FD is 10511872
via Connected, Serial1P 190.1.0.0/22, 1 successors, FD is 10511872
via Summary (10511872/0), Null0P 190.1.3.0/24, 1 successors, FD is 10639872
via 190.1.1.1 (10639872/128256), Serial1P 190.1.2.0/24, 1 successors, FD is 10537472
via 190.1.1.1 (10639872/128256), Serail1
BA C
D
e0
e1
s1
190.1.1.0/24
190.1.3.0/24
190.1.2.0/24
10.2.10.0/24
10.2.50.0/24
190.1.0.0/22
Advertised to A
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Router As topology table would show only the
summary route: Any packet destined for a network that is part of the
190.1.0.0/22 summary would be sent to Router B.
RTA#show ip eigrp topology
IP-EIGRP Topology Table for process 1
(output omitted)
P 190.1.0.0/22, 1 successors, FD is 11023872via 10.2.50.1 (11023872/10511872), Serial0
Manual Summarization Example
BA C
D
e0
e1
s1
190.1.1.0/24
190.1.3.0/24
190.1.2.0/24
10.2.10.0/24
10.2.50.0/24
190.1.0.0/22
Advertised to A
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Bandwidth OptimizationBy default, EIGRP will only consume up to 50% of a links
configured bandwidth. If a link in 256Kbps, then EIGRP traffic will use up to 128Kbps
Why would you want to change the default setting?
May be necessary when network apps require certain amounts of
bandwidth at all times. Sometimes, EIGRP traffic will require a certain level of bandwidth
availability.
Note: Changing EIGRPs bandwidth percentage has noeffect on user traffic.
Two commands to configure EIGRP traffic percentage.bandwidth
ip bandwidth-percent eigrp
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bandwidth Configuration
Thebandwidthcommand
Router(config-if)#bandwidth bandwidth
Configured on the interface where you want to adjustEIGRP traffic.
Whatever value is specified with thebandwidth
command, EIGRP always takes 50% of it (by default). Remember: The bandwidth command is only used by
routing protocolsit has no effect on user traffic whenthe protocol is EIGRP. The router does not use thiscommand for any other purpose.
For example, you have a 128kbps link and you onlywant EIGRP to use 16kbps.
Router(config-if)bandwidth 32EIGRP will use, at most, 50% of the configured bandwidth
User traffic will still be allowed to use at least 112kbps (128-16)
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AS #
The second way to modify how much bandwidth
EIGRP uses is to use the following command:Router(config-if)#ip bandwidth-percent eigrpAS-number percent
Use this command when you want to specify adifferent percentage than 50% of the configuredbandwidth.
For example, you have a 64kbps link and the bandwidthhas been set to 32kbps for metric calculation purposes.
However, you want EIGRP to be able to use an entire32kbps of the links 64kbps speed, if needed.
Router(config)#int s0
Router(config-if)#bandwidth 32
Router(config-if)#ip bandwidth-percent eigrp 123 100
bandwidth-percent Configuration
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NBMA ConfigurationsNBMA Configuration
Guidelines EIGRP should not exceed
the CIR of the hubs serialline (also called the accessline).
To do so is calledoversubscribing the link
Aggregate traffic of all linksto the hub should no exceedthe hubs access line speed.
Bandwidth on virtual circuitsmust be the same in bothdirections.
HubRouter
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Point-to-Point NBMAExample of point-to-point
Frame Relay with EIGRP Each spoke router has a
virtual circuit to the hub witha CIR of 256kbps.
This is an oversubscribedsituation.Why would you want to
oversubscribe the spokerouters?
To allow up to 256kbpsacross each spoke whentraffic from other spokes islight.
Configure the 10 subifs withbandwith of 154kbps soEIGRP will only use 50% ofthe subif when the NBMA is
saturated with user traffic.
256k
256k
256k
256k
256k 256k
256k
256k
256k
256k
Access Line1.544 Mbps
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Point-to-Point ConfigurationsHub_Router(config)#interface serial 0
Hub_Router(config-if)#encapsulation frame-relayHub_Router(config-if)#int serial0.1 point-to-point
Hub_Router(config-subif)#bandwidth 154
Hub_Router(config-subif)#int serial0.2 point-to-point
Hub_Router(config-subif)#bandwidth 154
. . .
Hub_Router(config-subif)#int serial0.10 point-to-pointHub_Router(config-subif)#bandwidth 154
256k
256k
256k
256k
256k 256k
256k
256k
256k
256k
Access Line1.544 Mbps
The above configurationinsures EIGRP never
uses more than 77kbpsfor EIGRP traffic
Each Spoke Router mustalso be configured withthe same bandwidth as
the Hub Router.
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Multipoint EIGRP
In point-to-multipoint configurations...
If the CIR of each Spoke Router is the same, set theaccess lines bandwidth to the sum of the CIRs
If the CIR of the Spoke Routers are different, which isthe usual case, either...
Take the lowest CIR and multiply it by the number of virtualcircuits. This causes higher bandwidth links to be underutilized.
Preferred Hybrid Solution: Use subinterfaces and configure likebandwidth virtual circuits on the same subinterface.
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EIGRP & IPX Networks
EIGRP can optimizes IPX updates.
By default, IPX RIP and EIGRP routes are redistributedinto each process.
If IPX RIP and EIGRP have the same hop count, the IPXRIP route is believed unless both routes came from the
same router.This ensure the router always believes an IPX server over a
Cisco router.
If EIGRP IPX is running on two neighbor routers, by
default on...Serial links, SAP updates are only sent when a change occurs
LAN links, SAP updates are sent periodically (60 sec)
You can configure incremental updates if...
all nodes out the interface are EIGRP peers and
the LAN link is not directly connected to an IPX server
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EIGRP IPX Configurations
EIGRP and IPX basic routing configurationsRouter(config)#ipx routing
Router(config)#ipx router eigrpAS
To disable IPX RIP updates for a particularnetwork
Since IPX RIP is on by default (no additionalconfigurations are needed), to disable updates for aspecific network...
Router(config)#ipx router rip
Router(config-ipx-router)#no network network-number
To configure incremental SAP updates on LANs...Router(config-if)#ipx sap-incremental eigrpAS[rsup-only]
rsup-only means IPX RIP routing is used. EIGRP is only used for
SAP updates. EIGRP routes are ignored.
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Monitoring EIGRP
Table of Contents
End Slide Show
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Monitoring EIGRP
Monitoring Command Description
show ip eigrp neighbors [typenumber][details]
displays the neighbor table; can specify interface; detailsexpands the output
show ip eigrp interfaces [type
number][AS][details]
displays info about each EIGRP interface; options can specify the
interface, AS, and expand the output
show ip eigrp topology [AS|[ip-
address ][mask]]
show ip eigrp topology
[active|pending|zero-successors]
show ip eigrp topology all-links
show ip eigrp traffic [AS]
displays the number of EIGRP packets sent and received sent
the last time the counter was cleared; use to view excessiveEIGRP routing updates
debug eigrp fsmObserve the feasible successor activity and determine if routes
are being installed and deleted by the EIGRP routing process
debug eigrp packet
Observe the transmission and receipt of EIGRP packets
including hellos, queries, updates, etc. Sequence numbers are
also displayed.
displays the topology table; extra options can fine tune the output;
for example:
- specify the AS and/or a specific ip address
- show only routes in the active state, pending convergence, or
routes with no successors
- show all routes, not just feasible successors, with the all-
links option
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Chapter 6 Lab Notes
Table of Contents
End Slide Show
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Lab NotesLab 6.7.1: Configuring EIGRP with IGRP
Build a router topology with EIGRP and IGRP routers Use the show ip route command to note differences in how
external routes are noted: The IGRP route table will denote EIGRP routes with an I
The EIGRP table will denote IGRP routes with a D EX
Lab 6.7.2: Configuring EIGRP Fault Tolerance Build an EIGRP topology and verify feasible successor
Turn of debug eigrp fsm & observe route flushing
Lab 6.7.3: Configuring EIGRP Summarization Configure topology with loopbacks
View outputs for auto and manual summarization
Lab 6.8.1: EIGRP Challenge Lab Four router lab with EIGRP and IGRP Ass
Capture running configs before and after summarization
Verify successful ping to every interface from all routers
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Table of Contents
End Slide Show
Acknowledgements