Sybex CCNA 640-802

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29 Οκτ 2013 (πριν από 3 χρόνια και 7 μήνες)

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Sybex CCNA 640
-
802

Chapter 7: EIGRP and OSPF

Instructor

& Todd Lammle

Chapter 7 Objectives


Enhanced IGRP


EIGRP tables


Configuring EIGRP


Verifying EIGRP


Open Shortest Path First


Configuring OSPF


Verifying OSPF


Configuring OSPF with wildcards


2

What Is Enhanced IGRP
(EIGRP)?


Enhanced IGRP supports:


Rapid convergence


Reduced bandwidth usage


Multiple network
-
layer support


Uses Diffused Update Algorithm (DUAL) to select
loop
-
free routes and enable fast convergence


Up to six unequal paths to a remote network (4 by
default)

Enhanced

IGRP

IPX

Routing

Protocols

AppleTalk

Routing Protocol

IP

Routing

Protocols

IPX

Routing

Protocols

AppleTalk

Routing Protocol

IP

Routing

Protocols

Comparing EIGRP and IGRP


Similar metric


Same load balancing


Improved convergence time


Reduced network overhead


Maximum hop count of 255 (100
default)


EIGRP can differentiate
between internal and external
routes

EIGRP for IP


No updates. Route updates sent only
when a change occurs


multicast on
224.0.0.10


Hello messages sent to neighbors every
5 seconds (60 seconds in most WANs)


Enhanced IGRP

EIGRP

EIGRP

hello

EIGRP Terminology

Neighbor Table

IP

Next Hop

Interface


Router

Topology Table

IP

Destination 1 Successor

Destination 1 Feasible Successor


Routing Table

IP

Destination 1 Successor


Note: A feasible successor is a backup route and stored in the
Topology table

EIGRP Tables


The neighbor table and topology table are
held in ram and are maintained through
the use of hello and update packets
.

Enhanced IGRP

EIGRP

EIGRP

hello

To see all feasible successor routes known to a router, use the
show
ip eigrp topology

command

Successor routes


Successor route is used by EIGRP to
forward traffic to a destination


A successor routes may be backed up
by a feasible successor route


Successor routes are stored in both the
topology table and the routing table

Routing Table

IP

Destination 1 Successor


Topology Table

IP

Destination 1 Successor

Destination 1 Feasible Successor


Choosing Routes


EIGRP uses a composite metric to pick the
best path: bandwidth and delay of the line


EIGRP can load balance across six
unequal cost paths to a remote network (4
by default)

IPX

19.2

T1

T1

T1

IPX

AppleTalk

IP

AppleTalk

IP

A

B

D

C

Configuring EIGRP for IP

172.16.10.0

10.110.1.0

192.168.0.0

AS=10

Router(config)#
router eigrp 10

Router(config
-
router)#
network 10.0.0.0

Router(config
-
router)#
network 172.16.0.0

192.168.0.0

A

C

B

Enable EIGRP


Assign networks

If you use the same AS number for EIGRP as IGRP,
EIGRP will automatically redistribute IGRP into
EIGRP

Redistribution

Redistribution is translating one type
of routing protocol into another.

Router D

Router B

Router A

Router C

EIGRP

IGRP

IGRP and EIGRP translate automatically, as long as they are both
using the same AS number

Route Path

Assuming all default parameters,
which route will RIP (v1 and v2)
take, and which route will EIGRP
take?

T1

T1

100BaseT

100BaseT

10BaseT

56K

Verifying Enhanced IGRP
Operation

show ip protocols

Router#


show ip route eigrp


Router#

show ip eigrp traffic



Router#


show ip eigrp neighbors


Router#


show ip eigrp topology


Router#


Displays the neighbors discovered by
IP Enhanced IGRP



Displays the IP Enhanced IGRP
topology table



Displays current Enhanced IGRP
entries in the routing table



Displays the parameters and current
state of the active routing protocol
process



Displays the number of IP Enhanced
IGRP packets sent and received

Show IP Route


-
D is for “Dual”


-
[90/2172] is the administrative distance and cost of
the route. The cost of the route is a composite metric
comprised from the bandwidth and delay of the line

P1R1#
sh ip route

[output cut]

Gateway of last resort is not set

D 192.168.30.0/24 [90/2172] via 192.168.20.2,00:04:36,
Serial0/0

C 192.168.10.0/24 is directly connected, FastEthernet0/0

D 192.168.40.0/24 [90/2681] via 192.168.20.2,00:04:36,
Serial0/0

C 192.168.20.0/24 is directly connected, Serial0/0

D 192.168.50.0/24 [90/2707] via 192.168.20.2,00:04:35,
Serial0/0

P1R1#


Open standard


Shortest path first (SPF) algorithm


Link
-
state routing protocol (vs. distance vector)


Can be used to route between AS’s

Introducing OSPF

OSPF Hierarchical Routing


Consists of areas and autonomous
systems


Minimizes routing update traffic


Supports VLSM


Unlimited hop count

Link State Vs. Distance Vector





Link State:


Provides common view of entire topology


Calculates shortest path


Utilizes event
-
triggered updates


Can be used to route between AS’s

Distance Vector:


Exchanges routing tables with neighbors


Utilizes frequent periodic updates

Types of OSPF Routers

Internal

Routers

Area 1

Area 2

ASBR and

Backbone

Router

Backbone/

Internal

Routers

ABR and

Backbone

Router

Backbone Area 0

ABR and

Backbone

Router

Internal

Routers


External


AS

Router(config
-
router)#
network
address mask
area

area
-
id

Assigns networks to a specific OSPF area

Router(config)#
router ospf process
-
id

Defines OSPF as the IP routing protocol

Note: The process ID is locally significant and is needed

to identify a unique instance of an OSPF database

Configuring Single Area OSPF

OSPF Example

hostname R3


router ospf 10

network 10.1.2.3 0.0.0.0 area 0

network 10.1.3.1 0.0.0.0 area 0

hostname R2


router ospf 20

network 10.0.0.0 0.255.255.255
area 0




hostname R1


router ospf 30

network 10.1.0.0 0.0.255.255
area 0

network 10.5.5.1 0.0.0.0 area 0


R3

R2

R1

10.1.2.0

10.1.1.0

10.5.5.0

Area 0

10.1.3.0

Router#
show ip ospf interface

Verifying the OSPF
Configuration


Displays area
-
ID and adjacency information

Router#
show ip protocols


Verifies that OSPF is configured

Router#
show ip route


Displays all the routes learned by the router

Router#
show ip ospf neighbor


Displays OSPF
-
neighbor information on a per
-
interface basis

OSFP Neighbors


OSPF uses hello packets to create
adjacencies and maintain connectivity
with neighbor routers


OSPF uses the multicast address
224.0.0.5


Hello?

224.0.0.5


Hello packets provides dynamic neighbor discovery


Hello Packets maintains neighbor relationships


Hello packets and LSA’s from other routers help build and maintain the
topological database

OSPF Terminology



Neighbor



Adjacency


Neighbors

Cost=6

ABR

BDR

DR

Non
-
DR

Adjacencies

Router ID (RID)

Each router in OSPF needs to be uniquely
identified to properly arrange them in the
Neighbor tables.

Electing the DR and BDR


OSPF sends Hellos which elect DRs and BDRs



Router form adjacencies with DRs and BDRs in a multi
-
access environment

Multicast Hellos are sent and compared

Router with Highest Priority is Elected as DR

Router with 2
nd

Highest Priority is Elected as BDR

Configuring Loopback Interfaces

Router ID (RID):


Number by which the router is known to OSPF


Default: The highest IP address on an active
interface at the moment of OSPF process startup


Can be overridden by a loopback interface: Highest
IP address of any active loopback interface


also
called a logical interface

Interface Priorities

What is the default OSPF interface priority?

Router# show ip ospf interface ethernet0/0

Ethernet0 is up, line protocol is up

Internet Address 192.168.1.137/29, Area 4

Process ID 19, Router ID 192.168.1.137, Network Type BROADCAST,

Cost: 10 Transmit Delay is 1 sec, State DR, Priority 1

Designated Router (ID) 192.168.1.137, Interface address 192.168.1.137

No backup designated router on this network

Timer intervals configured, Hello 10, Dead 40, Wait 40, Retransmit 5

Hello due in 00:00:06

Index 2/2, flood queue length 0

Next 0x0(0)/0x0(0)

Last flood scan length is 0, maximum is 0

Last flood scan time is 0 msec, maximum is 0 msec

Neighbor Count is 0, Adjacent neighbor count is 0

Suppress hello for 0 neighbor(s)


Ensuring your DR


What options can you configure that will
ensure that R2 will be the DR of the LAN
segment?

Configuring Wildcards

If you want to advertise a partial
octet (subnet), you need to use
wildcards.


0.0.0.0 means all octets match
exactly


0.0.0.255 means that the first
three match exactly, but the last
octet can be any value

After that, you must remember
your block sizes….

Wildcard

The wildcard address is always one less
than the block size….


192.168.10.8/30 = 0.0.0.3


192.168.10.48/28 = 0.0.0.15


192.168.10.96/27 = 0.0.0.31


192.168.10.128/26 = 0.0.0.63

Wildcard Configuration of the
Lab_B Router


Lab_A


E0: 192.168.30.1/24


S0: 172.16.10.5/30


Lab_B


E0: 192.168.40.1/24


S0: 192.168.10.10/30


S1: 192.168.10.6/30


Lab_C


E0: 192.168.50.1/24


S1: 172.16.10.9/30

Summary


Go through all the written and review
questions


Go over the answers with the class

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