Chapter 9 - EIGRP CCNA doc

Học viện mạng Bach Khoa - Website: www.bkacad.com 2Objectives • Describe the background and history of Enhanced Interior Gateway Routing Protocol EIGRP.. Học viện mạng Bach Khoa - Websi

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Chapter 9 - EIGRP

CCNA Exploration 4.0

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Học viện mạng Bach Khoa - Website: www.bkacad.com 2

Objectives

• Describe the background and history of Enhanced

Interior Gateway Routing Protocol (EIGRP).

• Examine the basic EIGRP configuration commands

and identify their purposes.

• Calculate the composite metric used by EIGRP.

• Describe the concepts and operation of DUAL.

• Describe the uses of additional configuration

commands in EIGRP.

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Introduction

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Introduction to EIGRP

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• Roots of EIGRP: IGRP

RIPv1’s limited hop count

 Delay (used by default)

 Reliability

IOS 12.2(13)T & 12.2(R1s4)S

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Enhanced Distance Vector Routing Protocol: EIGRP

(DUAL)

uses periodic updates

from the routing table, which includes the best path and any loop-free backup paths

DUAL will use a backup path if one exists in the topology table

absence of holddown timers and a system of coordinated route

uses periodic updates

routes; the best path to a

destination network

unavailable, the router must

wait for a new routing

update

holddown timers

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EIGRP Message Format

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EIGRP routing process.

EIGRP

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EIGRP

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Reliable Transport Protocol (RTP)

• Purpose of RTP

receive EIGRP packets

• Characteristics of RTP

– Involves both reliable & unreliable

delivery of EIGRP packet

 Reliable delivery requires acknowledgment from destination

 Unreliable delivery does not require an acknowledgement from destination

 Unicast

 Multicast: Using address 224.0.0.10

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• Hello packets

– Used to discover & form adjacencies with neighbors

EIGRP packet types

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Query & Reply packets

searching for networks

EIGRP packet types

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• Purpose of Hello Protocol

– To discover & establish adjacencies with neighbor routers

• Characteristics of hello protocol

 Most networks it is every 5 seconds

every 60 seconds

• Holdtime

router should wait before declaring a neighbor down

 Default holdtime: 3 times hello

interval

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EIGRP bounded updates

• Partial update

– A partial update includes only the route information that has

changed – the whole routing table is NOT sent

• Bounded update

will be notified of the change

bandwidth

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Diffusing Update Algorithm (DUAL)

• Provides for fast convergence time by keeping a list of loop-free backup routes

EIGRP routing algothrim - DUAL

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not encrypt the router's

routing table

EIGRP authentication

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Basic EIGRP Configuration

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Network Topology

of an ISP router

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Autonomous System (AS) & Process IDs

• This is a collection of networks under the control of a single authority

(reference RFC 1930).

• AS Numbers are assigned by IANA.

• Entities needing AS numbers

 ISP.

 Internet Backbone prodiers.

 Institutions connecting to other institutions using AS numbers.

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number actually functions as a

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The router eigrp command

– Router eigrp autonomous-system

process ID number (autonomous-system number)

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The network Command

– Enables interfaces to transmit & receive EIGRP updates

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• The network Command with a Wildcard Mask

specific subnets

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Verifying EIGRP

any updates can be sent or received

established adjacencies with neighbors is

show ip eigrp neighbors

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• The show ip protocols command is used to verify that EIGRP is enabled

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Examining the Routing Table

• The show ip route

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Introducing the Null0 Summary Route

– Null0 is not a physical interface

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automatically summarized by R1 & R3

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EIGRP Metric Calculation

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EIGRP Composite Metric & the K Values

– Bandwidth, delay, reliability, and load

values K1 K5

– All other K values = 0

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• Use the show

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Delay

measure of time it takes

for a packet to traverse a

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• Reliability (not a default EIGRP metric)

– A measure of the likelihood that a link will fail

– Measure dynamically & expressed as a fraction of 255 the higher the fraction the better the reliability

• Load (not a default EIGRP metric)

– A number that reflects how much traffic is using a link

255

– The lower the fraction the less the load on the link

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Using the Bandwidth Command

does not change the link’s

physical bandwidth

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and delay

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Calculated BW = reference BW / lowest BW(kbps)

Calculated Delay = the sum of outgoing interface delays

(Note: reference BW = 107)

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Diffusing Update Algorithm (DUAL)

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Successors and Feasible Successors

172.30.1.0

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Advertised or Destination Feasible Dist Reported Dist Neighbor

RD220 not< FD31

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• RTY is successor with a computed cost of 31.

• “31” is the Feasible Distance (FD).

• RTX is a feasible successor because its RD is less than or equal to the FD.

- RTX’s RD (30) is less than the FD (31).

RTZ is NOT Feasible Successor, FC:

RD220 not< FD31

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Example of a Loop

Cost=70 Cost=19

RTZ has a Reported Distance to RTA of 220 Since its Reported Distance is greater than RTA’s own Feasibile Distance of 31, RTA can’t trust that the route RTZ takes is somehow back through itself.

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DUAL Concepts

EIGRP Topology table

eigrp topology command

Topology Table: Successor & Feasible Successor

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• EIGRP Topology Table dissected

DUAL Concepts

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DUAL Concepts

Topology Table: No

Feasible Successor

• A feasible successor

may not be present

because the feasibility

condition may not be

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• Finite Sate Machine (FSM)

– An abstract machine that defines a set of possible states

something can go through, what event causes those

states and what events result form those states.

– FSMs are used to describe how a device, computer

program, or routing algorithm will react to a set of input

events.

DUAL Concepts

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Finite State Machines (FSM): with Feasible Successor

• To examine output from EIGRP’s finite state machine us

the debug eigrp fsm command.

DUAL Concepts

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Finite State Machines (FSM): without Feasible Successor

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More EIGRP Configuration

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More EIGRP Configurations

The Null0 Summary Route

• By default, EIGRP uses the Null0 interface to discard any packets

that match the parent route but do not match any of the child routes

route whenever both of the following conditions exist

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Disabling Automatic Summarization

• The auto-summary command permits EIGRP to

automatically summarize at major network boundaries

• The no auto-summary command is used to disable

automatic summarization

– This causes all EIGRP neighbors to send updates that

will not be automatically summarized

 this will cause changes to appear in both

» Routing tables

» Topology tables.

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• Disabling Automatic Summarization: topology table change

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Manual Summarization

• Manual summarization can include supernets

– Reason: EIGRP is a classless routing protocol & include

subnet mask in update

• Command used to configure manual summarization

– Router(config-if)# ip summary-address eigrp as-number

network-address subnet-mask

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• Configuring a summary route in EIGRP

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• Configuring a summary route in EIGRP

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EIGRP Default Routes

• “quad zero” static default route

outside the EIGRP domain/

• EIGRP & the “Quad zero” static default route

– Requires the use of the redistribute static command to

disseminate default route in EIGRP updates/

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Fine-Tuning EIGRP

• EIGRP bandwidth utilization

– By default, EIGRP uses only up to 50% of interface bandwidth for EIGRP information.

– The command to change the percentage of bandwidth used by EIGRP is

Router(config-if)# ip bandwidth-percent eigrp as-number percent

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– Hello intervals and hold times are configurable on a per-interface basis

Router(config-if)#ip hello-interval eigrp as-number seconds

value greater than or equal to the hello interval

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Configuring EIRGP authentication

• Step 1: Enter configuration mode for the interface on which you

want to enable authentication.

• Step 2: Specify MD5 authentication for EIGRP packets using the

ip authentication mode eigrp 100 md5 command.

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• Step 3: Enable the authentication of EIGRP packets with a key

specified in a key chain by using the ip authentication key-chain eigrp ASNumber key-chain command.

• Step 4: Enter the configuration mode for the key chain using the

key chain key-chain (key-chain can be different in each side).

• Step 5: Identify a key ID to use, and enter configuration mode for that key using the key key-id command.

Học viện mạng Cisco Bách Khoa - Website: www.ciscobachkhoa.com

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• Step 6: Identify the key string (password) for this key using the

key-string {key-string} command.

(key-string must be the same on both side of EIGRP routers)

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EIGRP redistribution

• Planning Redistribution

• Locate the boundary router between two routing processes.

• Determine which routing process is the core or backbone

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Configuring redistribution into EIGRP

• Use this command to redistribute routes into EIGRP:

external 2}] [metric metric-value] [route-map tag]

map-•RtrA(config)# router eigrp 100 RtrA(config-router)# redistribute ospf ?

<1-65535> Process ID

•RtrA(config-router)# redistribute ospf 1 ?

• match Redistribution of OSPF routes

• metric Metric for redistributed routes

• route-map Route map reference

• …

•<cr>

• Default metric is infinity

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Configuring redistribution into EIGRP

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• Describe the background and history of EIGRP.

• Describe the features and operation of EIGRP.

• Examine the basic EIGRP configuration commands and

identity their purposes.

• Calculate the composite metric used by EIGRP.

• Describe the concepts and operation of DUAL.

• Describe the uses of additional configuration commands in

EIGRP.

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Tiêu đề	Chapter 9 - EIGRP CCNA Exploration 4.0
Trường học	Học viện mạng Bach Khoa
Chuyên ngành	Networking
Thể loại	Document

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