eigrp fundamentals

11

Semester 5Semester 5

Chapter 6EIGRP

22

ObjectiveObjectiveUpon completion of this chapter, you will

be able to perform the following tasks:►Describe EIGRP features and operation►Explain how EIGRP discovers, chooses, and

maintains routes►Explain how EIGRP supports the use of VLSM

and route summarization►Explain how EIGRP operates in an NBMA

environment►Describe how EIGRP supports large networks►Configure and Verify EIGRP

33

TopicTopic

1. EIGRP Fundamentals2. EIGRP Features3. EIGRP Components4. EIGRP Operation5. Configuring EIGRP6. Monitoring EIGRP7. Summary/Question and Answer

44

EIGRP FundamentalEIGRP Fundamental

1. EIGRP Overview2. EIGRP and IGRP compatibility 3. EIGRP design 4. EIGRP support for Novell IPX and

AppleTalk 5. EIGRP terminology

55

EIGRP OverviewEIGRP OverviewCisco released EIGRP in 1994 as a

scalable, improved version routing protocol to replace IGRP.

EIGRP supports:►Rapid convergence►Reduced bandwidth usage►Multiple network-layer protocols

supported►Easy to configure….

66

EIGRP and IGRP compatibilityEIGRP and IGRP compatibility EIGRP uses a different metric calculation

►EIGRP scales IGRP's metric by a factor of 256. ►EIGRP uses a metric that is 32 bits long (IGRP 24-bit )

By multiplying or dividing by 256, EIGRP can easily exchange

information with IGRP.

77

EIGRP and IGRP compatibilityEIGRP and IGRP compatibility

Different hop-count limitation►EIGRP also imposes a maximum hop limit of

224 < IGRP's generous 255Similar with IGRP►Getting dissimilar routing protocols (RIP,

OSPF..) need to redistribute or add on configuration.

►Sharing, or redistribution, is automatic between IGRP and EIGRP if same AS number.

88

EIGRP design EIGRP design EIGRP acts like a link-state protocol when

updating neighbors and maintaining routing information.

EIGRP's advantages over simple distance-vector protocols :►Rapid convergence (because use Diffusing Update

Algorithm - DUAL)►Efficient use of bandwidth

Partial, bounded (incremental) updatesMinimal consumption of bandwidth when the network is

stable with small hello packets►Support for VLSM and CIDR►Multiple network-layer support and Independence

from routed protocols

99

EIGRP with IPXEIGRP with IPX

Redistribute IPX RIP and SAP information to improve overall performance► Take over for these two protocols. ► Router will receive routing and service updates and then update other

routers only when changes in occur: Routing updates occur as they would in any EIGRP network - using partial

updates. EIGRP sends SAP updates incrementally on all serial interfaces by default

► Advanced Metric, Hop from RIP, NLSP and SAP► Cisco IOS > 11.1 EIGRP can redistribute NLSP

1010

EIGRP with AppleTalkEIGRP with AppleTalkEIGRP can also take over for AppleTalk's

Routing Table Maintenance Protocol (RTMP - distance-vector routing protocol).

EIGRP redistributes AppleTalk routing information using event-driven updates.

Configurable composite metric to determine the best route to an AppleTalk network.

Remember:►AppleTalk clients expect RTMP information from local

routers.►EIGRP for AppleTalk should be run only on a

clientless network, such as a WAN link.

1111

EIGRP terminologyEIGRP terminologyKeep route and topology information readily in RAM

react quickly to changes. Neighbor table

► The lists adjacent routers, each protocol each table Topology Table

► Route entries for all destinations, each protocol each table Routing Table

► The best route from Topology table, each protocol each table Successor

► Primary route to reach destination► Kept in routing table► Multiple successors for a destination can be retained in the routing table

Feasible successor (FS)► Backup route► Kept in Topology Table► Multiple FS for a destination can be retained in the Topology table

1212

EIGRP FeaturesEIGRP Features

1. EIGRP technologies 2. Neighbor discovery and recovery 3. Reliable transport protocol 4. DUAL finite-state machine 5. Protocol-dependent modules

1313

EIGRP technologiesEIGRP technologies

Many new technologies are improvement in operating efficiency, rapidity of convergence, or functionality relative another Routing protocol

Four categories: 1.Neighbor discovery and recovery 2.Reliable Transport Protocol 3.DUAL finite-state machine 4.Protocol-specific modules

1414

Neighbor discovery and recoveryNeighbor discovery and recovery EIGRP routers actively establish

relationships with their neighbors same way that OSPF routers do.

EIGRP routers establish adjacencies with neighbor routers by using small hello packets (default every 5s or 60s).

By forming adjacencies, EIGRP routers do:►Dynamically learn of new routes that

join their network► Identify routers that become either

unreachable or inoperable►Rediscover routers that had

previously been unreachable

1515

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 the information!

Ack3Topology

Table

4

Here is my complete route information.Update5

Converged

Thanks for the information! 6

1616

Reliable transport protocol (RTP)Reliable transport protocol (RTP)

RTP,EIGRP own protocol, is a transport-layer protocol that can guarantee ordered delivery of EIGRP packets to all neighbors.

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

Reliable delivery of other routing information can actually speed convergence because EIGRP routers are not waiting for a timer to expire before they retransmit.

EIGRP can multicast and unicast to different peers simultaneously, allowing for maximum efficiency.

1717


EIGRP reliable packets are packets that requires explicit acknowledgement:►Update►Query►Reply

EIGRP unreliable packets are packets that do not require explicit acknowledgement:►Hello►Ack

1818


The router keeps a neighbor list and a retransmission list for every neighbor

Each reliable packet (update, query, reply) will be retransmitted when packet is not acknowledged

Neighbor relationship is reset when retry limit (limit = 16) for reliable packets is reached This information is required to allow EIGRP to maintain a loop-free topology at all times.

1919


EIGRP transport has window size of one (stop and wait mechanism)►Every single reliable packet needs to be

acknowledged before the next sequenced packet can be sent

►If one or more peers are slow in acknowledging, all other peers suffer from this

Solution: The non acknowledged multicast packet will be retransmitted as a unicast to the slow neighbor

2020

DUAL finite-state machine (DFS)DUAL finite-state machine (DFS)

Diffusing Update Algorithm (DUAL) EIGRP's route-calculation engine.

DFS:►Tracks all routes advertised by neighbors.►Lowest-cost paths are inserted by the DUAL

protocol into the routing table.►Select loop-free path using a successor and

remember any feasible successors.If successor lost: Use feasible successorIf no feasible successor: Query neighbors and

recomputed new successor

2121

DUAL ExampleDUAL Example

E EIGRP FD AD Topology (a) 3 (fd)

via D 3 2 (Successor)via C 4 3

D EIGRP FD AD Topology(a) 2 (fd)

via B 2 1 (Successor)via C 5 3

C EIGRP FD AD Topology(a) 3 (fd)

via B 3 1 (Successor)via D 4 2 (fs)via E 4 3

(1)

(1)

(1)

(1)

(2)(2)

(a)

A

E

D

C

B

2222








(1)

(1)

(1)

(1)

(2)(2)

(a)

A

E

D

C

B XX

2323


Q Q(1)

(1)

(1)

(2)(2)

(a)

A

E

D

C

B



D EIGRP FD AD Topology(a) **ACTIVE** -1 (fd)

via E (q)via C 5 3 (q)


via B 3 1 (Successor)via Dvia E 4 3

2424


R

Q

(1)

(1)

(1)

(2)(2)

(a)

A

E

D

C

B

E EIGRP FD AD Topology (a) **ACTIVE** -1 (fd)

via D via C 4 3 (q)


via E (q)via C 5 3


via B 3 1 (Successor)via D via E

2525


R

(1)

(1)

(1)

(2)(2)

(a)

A

E

D

C

B


via C 4 3 (Successor)via D


via E (q)via C 5 3


via B 3 1 (Successor)via Dvia E

2626


R

(1)

(1)

(1)

(2)(2)

(a)

A

E

B




via C 5 3 (Successor)via E 5 4 (Successor)



D

C

2727


(1)

(1)

(1)

(2)(2)

(a)

A

E

D

C

B







2828

DUAL Example (Start) DUAL Example (Start)

(1)

(1)

(1)

(1)

(2)(2)

(a)

A

E

D

C

B







2929

DUAL Example (End)DUAL Example (End)

(1)

(1)

(1)

(2)(2)

(a)

A

E

D

C

B







3030

Protocol-dependent modules (PDM)Protocol-dependent modules (PDM)PDM is responsible for all functions

related to its specific routed protocol

3131

Protocol-dependent modules (PDM)Protocol-dependent modules (PDM)PDM can ►Support for routed protocols such as IP, IPX, and

AppleTalk ►Easily adapt to new or revised routed protocols

Sending and receiving EIGRP packets that bear IP data►Notifying DUAL of new IP routing information that is

received ►Maintaining the results of DUAL's routing decisions in

the IP routing table ►Redistributing routing information that was learned by

other IP-capable routing protocols

3232

EIGRP ComponentsEIGRP Components

Relies on several different kinds of packets to maintain its various tables and establish complex relationships with neighbor routers

The 5 EIGRP packet types are listed here: ►Hello : Establish neighbor relationships►Acknowledgment :Acknowledgement of a reliable

packet►Update : Send routing updates►Query : Ask neighbors about routing information►Reply : Response to query about routing information

3333

EIGRP Components - EIGRP Components - HelloHelloUse for Discover, verify & rediscover neighbor

routers.Hello packets are

multicast : 224.0.0.10Send hellos at a hello

interval. Default value:EIGRP routers do not receive each other's hellos

for a hold time interval (3 times hello interval):►Rediscovery occurs and then re-establish

communication.►DUAL must step in to re-evaluate the routing table

No need same hello and dead intervals to communicate.

3434

EIGRP Components – EIGRP Components – AcknowledgmentAcknowledgment

To indicate receipt of any EIGRP packet during a "reliable" exchange.

Recall that RTP can provide reliable communication between EIGRP hosts

"dataless" hello packets unicast.Hello packets are always sent unreliably

and thus do not require acknowledgment

3535

EIGRP Components – EIGRP Components – UpdateUpdate New neighbor:►Use when a router discovers a new neighbor.►EIGRP router sends unicast update packets

(maybe more than one) to new neighbor it can add to its topology table.

Old neighbor:►Use when a router detects a topology change ►Sends a multicast update packet to all

neighborsUpdate packets are sent reliably

3636

EIGRP Components - EIGRP Components - Query and ReplyQuery and Reply

EIGRP router loses its successor and cannot find a feasible successor for a route:►DUAL places the route in the active state►Send multicasts a query to all neighbors for searching

a successor to destination.►Neighbors must send unicast replies that either

provide information on successors or indicate that no successor information is available

Both packet types are sent reliably

A B

Need specific information from B

query packets - multicast

reply packet - unicast

3737

EIGRP tablesEIGRP tables

DUAL can select alternate routes based on the tables kept by EIGRP

EIGRP router can track all the routing information in an AS, not just the "best" routes

EIGRP have 3 tables:►neighbor table►routing table►topology table

3838

EIGRP tablesEIGRP tables – – NeighborNeighbor

Neighbor relationships tracked in the neighbor table is the basis for all the EIGRP routing update and convergence activity.

Contains information about adjacent neighboring, new neighbor is discovered New entry.

Is used to support reliable, sequenced delivery of packets

3939

EIGRP tables – EIGRP tables – NeighborNeighbor

Neighbor address (Address)►The network-layer address of the neighbor

router

4040


Hold time (Hold Uptime) ►Interval to wait without receiving anything

from a neighbor before considering the link unavailable

►EIGRP packets received after the first hello will reset the timer

4141


Smooth Round-Trip Timer (SRTT)►Average time that it takes to send and receive

packets from a neighbor.►This timer is used to determine the retransmit

interval (RTO)

4242


Queue count (Q Cnt)►Number of packets waiting in queue to be

sent►Q Cnt:

=0: No EIGRP packets in the queue>0:May be a congestion problem at the router

4343

EIGRP tablesEIGRP tables – – RoutingRouting

Contains the routes installed by DUAL as the best loop-free paths to a given destination.

Maintain up to four routes (can be of equal or unequal cost) per destination

Maintain a separate routing table for each routed protocol.

4444

EIGRP tablesEIGRP tables – – TopologyTopology

4545


Store all the information it needs to calculate a set of distances and vectors to all reachable destinations

Maintains a separate topology table for each routed protocol

Is made up of all the EIGRP routing tables in the autonomous system.

By tracking this information, EIGRP routers can find alternate routes quickly

4646


Topology table have:►Feasible distance (FD is xxxx)►Route source (via xxx.xxx.xxx.xxx)►Reported distance (RD)

4747


RTA's routing table includes a route to Z via RTB (current successor). RTA Should be have at least one successor for Z for DUAL to place it in the routing table

RTC claims to have a route to Z with the exact same metric as RTB DUAL will install a second route to Z.

RTA's other neighbors that advertise a loop-free route to Z (with RD > the best-route metric and < FD) will be identified as feasible successors in the topology table.►Note: RD = Reported Distance, FD = Feasible Distance.

4848

EIGRP tablesEIGRP tables – – TopologyTopologySuccessor down DUAL identify a FS

from the topology table and install a new route to the destination.

No FS to the destination exist, DUAL places the route in the active state

Entries in the topology table can be in one of two states: ►Active or Passive►These states identify the status of the route

indicated by the entry rather than the status of the entry itself.

4949

EIGRP tablesEIGRP tables – – TopologyTopologyA passive route is one that is stable and

available for use. An active route is a route in the process of being

recomputed by DUAL. ►Re-computation happens if a route becomes

unavailable and DUAL can not find any feasible successors.

►When this occurs, the router must ask neighbors for help in finding a new, loop-free path (feasible successors) to the destination.

►Neighbor routers are compelled to reply to this query:If a neighbor has a route, it will reply with

information about the successor(s). If not, the neighbor notifies the sender that it does

not have a route to the destination either.

5050

"Stuck in Active" (SIA) Routes"Stuck in Active" (SIA) Routes

DUAL always tries to find a feasible successor before resorting to a re-computation. If a feasible successor is available, DUAL can quickly install the new route and avoid re-computation.

The route(s) in "stuck in active" state : If one or more routers to which a query is sent do not respond with a reply within the active time of 180 seconds (3 minutes).

EIGRP clears the neighbors that did not send a reply and logs a "stuck in active" error message for the route(s) that went active.

5151

Route tagging with EIGRPRoute tagging with EIGRP

EIGRP classifies routes as either internal or external EIGRP uses route tagging to add special tags to each route

Tags identify route as :►Internal ►External ►Other

information

5252

Route tagging with EIGRPRoute tagging with EIGRP

Static routes are external routesExternal routes are included in the topology

table and are tagged with the following information:1.The router ID of the EIGRP router that redistributed

the route into the EIGRP network 2.The AS number of the destination 3.The protocol used in that external network 4.The cost or metric received from that external

protocol 5.The configurable administrator tag

Tag to be any number between 0 and 255

5353

EIGRP Operation EIGRP Operation

DUAL's sophisticated algorithm results in EIGRP's exceptionally fast convergence

5454

EIGRP OperationEIGRP Operation RTA choose RTY = Successor (lowest computed cost) 31 = FD to Network 24 RTY down RTA try to use FS.

5555

EIGRP OperationEIGRP Operation

RTA follows a three-step process:1. Determine which neighbors have a RD < FD

to network 24 RTX's RD is 302. Determine the minimum computed cost to

Network 24 : RTX is 40 RTX provides the lowest computed cost.

3. Determine whether any routers that met the criterion in Step 1 also met the criterion in Step 2. RTX has done both, so it is the feasible successor.

5656

EIGRP OperationEIGRP Operation RTY down, RTA uses RTX (FS) forward packets to Network 24 If RTX also becomes unavailable:

► RTZ cannot be a feasible successor because RD =220 > FD=31 And The FD can change only during an active-to-passive transition

DUAL has been performing what is called a local computationRTA cannot find any FS transitions passive to active state queries its neighbors diffusing computation Network 24 is active state the FD is reset RTA to at last accept RTZ as the successor

5757

Configuring EIGRPConfiguring EIGRP

1. Configuring EIGRP for IP networks 2. EIGRP and the bandwidth command and The

bandwidth-percent command 3. Configuring EIGRP for IPX networks 4. Controlling SAP updates 5. Summarizing EIGRP routes for IP 6. Variance

5858

For IP networksFor IP networks

1. router(config)# router eigrp autonomous-system-number► AS much match all router inside AS

2. router(config-router)# network network-number► Network number only for connected network

3. router(config-if)# bandwidth kilobits ► Serial interface link use (if not Router take default)

router(config-if)# eigrp log-neighbor-changes► Enables the logging of neighbor adjacency changes

5959

For IP networksFor IP networks

6060

EIGRP Bandwidth UtilizationEIGRP Bandwidth Utilization

Specifies what percentage of bandwidth EIGRP packets will be able to utilize on this interface

Uses up to 50% of the link bandwidth for EIGRP packets, by default ►Used for greater EIGRP load control

ip bandwidth-percent eigrp as-number percent ipx bandwidth-percent eigrp appletalk eigrp-bandwidth-percent

6161

EIGRP & Bandwidth over WANEIGRP & Bandwidth over WAN

EIGRP supports different WAN links►Point-to-point►NBMA

MultipointPoint-to-point

EIGRP configurations must address►Bandwidth utilization►Overhead traffic associated with router

operation

6262

Bandwidth over WAN InterfacesBandwidth over WAN Interfaces

Bandwidth utilization over point-to-point subinterfaces using Frame Relay►Treats bandwidth as T1, by default►Best practice is to manually configure

bandwidth as the CIR of the PVC

6363


Bandwidth over multipoint Frame Relay, ATM, SMDS, and ISDN PRI:►EIGRP uses the bandwidth on the main

interface divided by the number of neighbors on that interface to get the bandwidth information per neighbor

6464


Each PVC might have a different CIR, this might create an EIGRP packet pacing problem►Multipoint interfaces:

Convert to point-to-point configuration, orManually configure bandwidth =

(lowest CIR x number of PVCs)

6565

EIGRP WAN Configuration — Pure EIGRP WAN Configuration — Pure MultipointMultipoint

CIR 56

C

EF G

H

FrameRelay

S0

CIR 56 CIR 56

CIR 56

T1

interface serial 0 encap frame-relay bandwidth 224

• All VCs share bandwidth evenly: 4 x 56 = 224

6666

EIGRP WAN Configuration — Hybrid EIGRP WAN Configuration — Hybrid MultipointMultipoint

CIR 256BW 224

C

EF G

H

FrameRelay

S0

CIR 256BW 224

CIR 256BW 224

CIR 56BW 56

T1

• Lowest CIR x # of VC: 56 x 4 = 224

interface serial 0 encap frame-relay bandwidth 224

6767

EIGRP WAN Configuration— Hybrid EIGRP WAN Configuration— Hybrid Multipoint (Preferred)Multipoint (Preferred)

CIR 256BW 256

C

EF G

H

FrameRelay

S0

CIR 256BW 256

CIR 256BW 256

CIR 56BW 56

T1

interface serial 0.1 multipoint bandwidth 768

interface serial 0.2 point-to-point bandwidth 56

• Configure lowest CIR VC as point-to-point, specify BW = CIR• Configure higher CIR VCs as multipoint, combine CIRs

S0.1S0.2

6868

EIGRP WAN Configuration — Pure EIGRP WAN Configuration — Pure Point-to-PointPoint-to-Point

CIR 56BW 25

C

EF G

H

FrameRelay

S0

CIR 56BW 25

CIR 56BW 25

CIR 56BW 25

256

interface serial 0.1 point-to-point bandwidth 25 ip bandwidth-percent eigrp 63 110 - - - - interface serial 0.10 point-to-point bandwidth 25 ip bandwidth-percent eigrp 63 110

• Configure each VC as point-to-point, specify BW = 1/10 of link capacity• Increase EIGRP utilization to 50% of actual VC capacity

interface serial 0 bandwidth 25 ip bandwidth-percent eigrp 63 110

Hub and Spokewith 10x VCs

6969

For IPX networks & SAP updateFor IPX networks & SAP update

7070

For IPX networks & SAP updateFor IPX networks & SAP update Enable EIGRP for IPX, perform the

following steps:► Enable IPX routing: router(config)# ipx routing► Define EIGRP as the IPX routing protocol:

router(config-router)# ipx router {eigrp as-number | rip}

► Indicate networks: router(config-ipx-router)# network network-number

► (Optional) If IPX RIP is also operating on the router, remove RIP:router(config-ipx-router)# no network network-number

7171

For IPX networks & SAP updateFor IPX networks & SAP updateBy Default, Cisco routers redistribute IPX

RIP routes IPX EIGRP routes.RIP route to a destination with a hop count

of 1 is always preferred over an EIGRP route with a hop count of 1 (exception if both the RIP and EIGRP updates were received from the same router)

Controlling IPX RIP►RouterRouter: EIGRP►LAN Router:RIP(default)

7272

For IPX networks & SAP updateFor IPX networks & SAP update

To reduce the amount of bandwidth required to send SAP updates periodically:► router(config-if)#ipx sap-

incremental eigrp as-number [rsup-only]

► rsup-only: Indicate on this interface the

system uses EIGRP to carry reliable SAP update information only.

RIP routing updates are used EIGRP routing updates are

ignored

7373

Summarizing EIGRP routes – Summarizing EIGRP routes – AutoAutoEIGRP automatically summarizes routes at the

classfulIf you have discontiguous subnetworks Auto-

summarizes need disable

7474

Summarizing EIGRP routes – Summarizing EIGRP routes – ManualManual

router(config-if)#ip summary-address eigrp autonomous-system-number ip-address mask administrative-distance

Example:RTC(config)#router eigrp 2446RTC(config-router)#no auto-summaryRTC(config-router)#exitRTC(config)#interface serial0RTC(config-if)#ip summary-address eigrp 2446 2.1.0.0 255.255.0.0

7575

EIGRP Load BalancingEIGRP Load Balancing

Routes with metric equal to the minimum metric will be installed in the routing table (equal-cost load balancing)

Up to six entries in the routing table for the same destination►Number of entries is configurable►Default is four

7676

EIGRP Unequal-Cost Load BalancingEIGRP Unequal-Cost Load Balancing

EIGRP offers unequal-cost load balancing►variance command

Variance allows the router to include routes with a metric smaller than multiplier times the minimum metric route to that destination►Multiplier is the number specified by the

variance command

7777

10

20

10

10

20

25variance 2

Variance ExampleVariance Example

Router E will choose Router C to get to Network Z because FD = 20

With variance of 2, Router E will also choose Router B to get to Network Z (20 + 10) < (2 x [FD])

Router D will not be used to get to Network Z (45 > 40)

Network Z(config)#

AE

D

C

B

7878

Verify EIGRP with Verify EIGRP with Show Show commandcommandCommand 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 ip eigrp topology EXEC command. Also used to determine DUAL states & debug possible DUAL problems.

Show ip eigrp topology [active | pending | zero-successor]

Depending on keyword is used. Display all routes in the topology table that are either active, pending or without 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.

7979

Verify EIGRP with Verify EIGRP with Debug Debug commandcommandCommand Description

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

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

debug eigrp neighbor Displays the EIGRP neighbor interactiondebug ip eigrp route Displays advertisements and changes EIGRP

makes to the routing tabledebug 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

8080

SummarySummaryEIGRP, a routing protocol developed by

Ciscoadvanced distance-vector routing protocol

that uses the DUAL algorithmMajor feature:►Rapid convergence converges rapidly

based-on DUAL►Reduced bandwidth usage summarizes

routes, performs incremental updates►Multiple network-layer support IP, IPX, and

AppleTalk traffic

8181

Remember all EIGRP FeatureRemember all EIGRP Feature1. Advanced distance vector2. 100% loop free3. Fast convergence4. Easy configuration5. Less network design constraints than OSPF6. Incremental updates7. Supports VLSM and discontiguous networks8. Classless routing9. Compatible with existing IGRP networks10.Protocol independent (supports IP, IPX and

AppleTalk)

8282

EIGRP Scalability RulesEIGRP Scalability Rules

EIGRP is a very scalable routing protocol if proper design methods are used:►Good allocation of address space: Each

region should have a contiguous address space so route summarization is possible

►Have a tiered network design model

8383

Core

TokenRing

TokenRing

3.3.4.01.1.1.0

3.3.4.0

1.1.4.0

3.3.3.0

2.2.1.0

1.1.3.0

3.3.1.0

1.1.2.02.2.3.0

2.2.2.0

TokenRing

TokenRing

TokenRing

TokenRing

1.1.1.01.1.2.02.2.3.03.3.4.0

2.2.1.03.3.2.03.3.3.01.1.4.0

3.3.1.02.2.2.01.1.3.0

Nonscalable Network — ExampleNonscalable Network — Example

Bad addressing scheme►Subnets are everywhere throughout entire network

Queries not bounded

8484

Core

3.0.0.0

2.0.0.0

TokenRing

TokenRing

1.1.4.01.1.1.0

3.3.4.0

3.3.4.0

3.3.3.0

3.3.1.0

2.2.3.0

2.2.1.0

1.1.3.0

1.0.0.0

TokenRing

TokenRing

TokenRing

TokenRing

Scalable Network — ExampleScalable Network — Example

Readdress the network Each region has its own block of addresses

Queries bounded by using ip summary-address eigrp command

1.1.2.0

2.2.2.0

8585

Regional Office

Remote Office

Summarized Routes

Summarized RoutesSummarized Routes

Summarized Routes

Summarized Routes Summarized Routes

Tiered Network DesignTiered Network Design

OtherRegions

Core

OtherRegions

OtherRegions

OtherRegions

8686

More EIGRP Scalability RulesMore EIGRP Scalability Rules

Proper network resources:►Sufficient memory on the router►Sufficient bandwidth on WAN interfaces

Proper configuration of the bandwidth statement over WAN interfaces, especially over Frame Relay

8787

Question/AnswerQuestion/Answer

1. How are IGRP and EIGRP different in their metric calculation?

2. Why are EIGRP routing updates described as “reliable?”

3. What does it mean when a route is marked as a feasible successor?

4. What is the recommended practice for configuring bandwidth on a Frame Relay point-to-point subinterface?

8888

Question/AnswerQuestion/Answer Matching terms with statements. Place the letter of the description in front

of the term that the statement describes. A statement may describe several terms.

_____ 1. Successor A) A network protocol that EIGRP supports

_____ 2. FS B) A table that contains feasible successor information

_____ 3. Hello C) Administrative distance determines routing information that is included in this table.

_____ 4. Topology table D) A neighbor router that has the best path to a destination

_____ 5. IP E) A neighbor router that has the best alternative path to a destination

_____ 6. Update F) An algorithm used by EIGRP that assures fast convergence

_____ 7. AppleTalk G) A multicast packet used to discover neighbors

_____ 8. Routing table H) A packet sent by EIGRP routers when a new neighbor is discovered and when a change occurs

_____ 9. DUAL _____ 10. IPX

eigrp fundamentals

Documents

eigrp scalability

lowest computed

0token ringtoken

diffusing

vector routing

ipx networks

eigrp routing

reliable transport