IIUSA – Internet Institute - AskTOP.net

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Oct 28, 2013 (3 years and 10 months ago)

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IIUSA


Internet Institute

Switches & Routers

IIUSA


Internet Institute

Section Objectives


Overview of Switches and Routers in a
Network Environment


Switch Configuration


Routing Basics and Configuration


Displaying Router Information


Troubleshooting Routers and Switches

IIUSA


Internet Institute

Layer 3 (IP) Basics


Provides ability to address devices with a
logical address and route traffic not locally
attached


Logical addresses are applied to source and
destination nodes or devices


Paths are determined to forward data from a
local device to a remote device on another
network

IIUSA


Internet Institute

Router Functionality

Network A

Network B

Routing Table

Network A e0

Network B e1

e0

e1

Routers Separate Broadcast Domains

IIUSA


Internet Institute

Why a Logical Address


Hierarchical addresses provide reachability
across boundaries called subnets


Similar to the phone system with area codes
to differentiate geographical regions or zip
codes to indicate different cities and towns


A hierarchical logical computer address
contains a network identifier and host or
unit identifier

IIUSA


Internet Institute

Network Segments


The size of a network dictates traffic load and
potential for overload


As growth overwhelms a network (similar to cars
crowding a highway), segments can be created to
off load traffic


Each new segment is autonomous of other
network segments


Without segmentation, all addressing would be
done through a flat addressing scheme (MAC
addressing) overwhelming segmentation discovery
devices (routers)

IIUSA


Internet Institute

Connectivity Between Segments


Segments can communicate through devices
that determine a path from one network to
another over communications lines


Devices (routers) can determine the best
path in the case of multiple paths


Paths or routes are stored in routing tables


172.16.0.0/24 is subnetted, 1 subnets

C 172.16.1.0 is directly connected, Ethernet0


10.0.0.0/24 is subnetted, 2 subnets

R 10.2.2.0 [120/1] via 10.1.1.2, 00:00:07, Serial2

C 10.1.1.0 is directly connected, Serial2

R 192.168.1.0/24 [120/2] via 10.1.1.2, 00:00:07, Serial2


Portion of a

Routing Table

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Internet Institute

Network Layer Addressing


Routers use a portion of the address to
determination Network identification


All hosts or devices within a given network
segment are identified by a host portion of
the address


IP Addresses 172.16.10.100

Network ID

Host ID

IIUSA


Internet Institute

Path Determination


Network layer determines BEST path from
source to destination


A router examines reported paths over links,
determining best path from metrics
associated with each path

Best Path

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Internet Institute

IP Header Detail

Data

Version
4

Header Length
4

Type of Service
8

Total Length
16

Identification
16

Flags
3

Fragment Offset
13

Time to Live
8

Protocol (Upper Level)
8

Header Checksum
16

Source

IP Address
32

Destination

IP Address
32

IP Options
Variable

Data

Padding (If Needed)

IIUSA


Internet Institute

IP Address Numbering


IP Addresses are 32 bits in length

172

16

122

204

.

.

.

Network

Host

Each Octet is 8 bits in length, representing a byte

10101100

00010000

01111010

11001100

IIUSA


Internet Institute

Converting IP Addresses from Binary to
Decimal

1

1

1

1

1

1

1

1

128

64

32

16

8

4

2

1

8 Bits

255 Decimal Value

Note: All 0s indicates a decimal 0, totaling 256 Decimal Values

IIUSA


Internet Institute

Conversion Example

1

0

1

1

0

1

0

1

128

64

32

16

8

4

2

1

8 Bits

255 Decimal Value


128

+ 32

+ 16

+ 4

+ 1


181

IIUSA


Internet Institute

IP Classes

H

H

H

N

H

H

N

N

N

H

N

N

Class A

Class B

Class C

-

Network numbers are assigned by ARIN

-

Host numbers assigned by Network Administrators

IIUSA


Internet Institute

Class A Notes


Address range 1 to 126


Address 10 is reserved as a private address


Address 127 is reserved for loopback
purposes


First bit begins with a 0 (zero)

H

H

H

N

0

IIUSA


Internet Institute

Class B Notes


Address range 128 to 191


Address 172.16 to 172.31 is reserved as a
private address range


First two bits begin with a 10

H

H

N

N

10

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Internet Institute

Class C Notes


Address range 192 to 223


Address 192.168 is reserved as a private
address range


First three bits begin with a 110

N

H

N

N

110

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Internet Institute

Reserved Address Space


0s (zeros) in the host portion of the address
space is reserved for the
network number


Example: 172.16.0.0


1s in the host portion of the address is
reserved for the
broadcast address


Example: 172.16.255.255


IIUSA


Internet Institute

A Case for Subnetting


The original IP addressing scheme was sufficient
for the early days of the internetworking
environment


As the Internet grew in the 1990s, addressing,
using classful addressing became impractical


Subnetting (classless) addressing became the
answer for address space depletion

IIUSA


Internet Institute

Subnetting


Subnetting borrows host bits to increase the
number of networks


The number of hosts is reduced in
proportion to the number of bits borrowed

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Internet Institute

A Subnetted Network

Original Network 172.16.0.0

172.16.1.0

172.16.2.0

172.16.3.0

172.16.4.0

172.16.5.0

IIUSA


Internet Institute

16

Network

Host

172

0

0

10101100

11111111

10101100

00010000

11111111

00010000

00000000

00000000

10100000

00000000

00000000


Subnets not in use

the default

00000010

Subnet Mask without Subnets

172.16.2.160


255.255.0.0

Network

Number

Subnet Mask

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Internet Institute


Network number extended by eight bits

Subnet Mask with Subnets

16

Network

Host

172.16.2.160


255.255.
255
.0

172

2

0

10101100

11111111

10101100

00010000

11111111

00010000

11111111

00000010

10100000

00000000

00000000

00000010

Subnet

Network

Number

128

192

224

240

248

252

254

255

IIUSA


Internet Institute


Defining a Subnet Mask

Convert the Number of Segments to Binary

Count the Number of Required Bits

Convert the Required Number of Bits to Decimal

(High Order)

1

2

3

Example of Class B Address

Number of Subnets

Binary Value

Convert to Decimal

6

0 0 0 0 0
1 1 0

= 6

(3 Bits)

4+2

255 . 255 .

224

. 0

11111111

11111111

111
00000

00000000

Subnet Mask

Ignore the first bit borrowed, add the additional bits borrowed to
determine the number of new subnets

IIUSA


Internet Institute


Defining Subnet IDs

255

255

224

0

1 1 1 1 1 1 1 1

1 1 1 1 1 1 1 1

1 1 1

0 0 0 0 0

0 0 0 0 0 0 0 0

000
00000 = 0

001
00000 = 32

010
00000 = 64

011
00000 = 96

100
00000 = 128

101
00000 = 160

110
00000 = 192

111
00000 = 224

1

2

3

Evaluate the bit patterns established

within the subnetted region

IIUSA


Internet Institute

Shortcut to Defining Subnet IDs

List the Number of Bits (High Order) Used for

Subnet Mask

Convert the Bit with the Lowest Value to Decimal

Increment the Value for Each Bit Combination

11000000

64

0

+ 64

=
64

+ 64

=
128

+ 64

192

w
.
x
.
64
.1

w
.
x
.127.254

w
.
x
.
128
.1

w
.
x
.191.254

1

2

3

IIUSA


Internet Institute

Defining Host IDs for a Subnet

Subnet IDs

Host ID Range

Invalid

x.y
.
32
.
1



x.y
.
63
.
254

x.y
.
64
.
1



x.y
.
95
.
254

x.y
.
96
.
1



x.y
.
127
.
254

x.y
.
128
.
1



x.y
.
159
.
254

x.y
.
160
.
1



x.y
.
191
.
254

x.y
.
192
.
1



x.y.
223
.
254

Invalid

000
00000 = 0

001
00000 =
32

010
00000 =
64

011
00000 =
96

100
00000 =
128

101
00000 =
160

110
00000 =
192

111
00000 = 224


Each Subnet ID Indicates the Beginning Value in a Host Range


The Ending Value Is One Less Than the Beginning Value of the Next
Subnet ID

IIUSA


Internet Institute

Network to Network Connectivity

172.16.1.0

172.16.2.0

172.16.3.0

172.16.4.0



Router strips off the data link header



Examines the network layer address



Consults the routing table to find the interface for the network

1

2

3

IIUSA


Internet Institute

Network
-
Layer Protocol Operations

Each router provides its services to support upper
-
layer functions

X

Y

A

B

C

A

B

C

Physical

Data Link

Network

Physical

Data Link

Network

Physical

Data Link

Network

Physical

Data Link

Network

Transport

Session

Presentation

Application

Physical

Data Link

Network

Transport

Session

Presentation

Application

IIUSA


Internet Institute

Routed Versus Routing Protocols


Routed Protocols



Any network protocol
run on a workstation as a part of the
network operating system that provides
networking capabilities (Ex: TCP/IP)


Routing Protocols



Protocols run on a
router to provide the ability for the router to
share path information (Ex: RIP, IGRP)

IIUSA


Internet Institute

Routing Protocols


Interior Routing Protocols



support the
sharing of routes or paths within the internal
internetwork



(Ex: RIP, IGRP, EIGRP, OSPF)


Exterior Routing Protocols



support the
sharing of routes or paths across large
internetworks, such as the Internet



(Ex: BGP and EGP)

IIUSA


Internet Institute

Routing Metrics


All routing protocols utilize
metrics

to
characterize best path information


Hop Count


Bandwidth


Delay


Load


Reliability


Ticks (Novell)


Cost


generic definition of metric information

IIUSA


Internet Institute

Static versus Dynamic Routes


Static

routes are established by a network
administrator and manually input directly
into the routing table


Dynamic

routes are learned through the use
of a Routing Protocol. Dynamic routes are
adaptive. Changes to path availability or
establishment of new paths are
automatically shared with other routers

IIUSA


Internet Institute

Routers


A Router is a computer, with similar functionality


Forwards packets, from incoming interface to
outgoing interfaced, based on best path as
determined by routes available in the routers
Routing Table


Segments a LAN into separate Broadcast Domains


Must be used when connecting LANs across wide
area network environment

IIUSA


Internet Institute

Typical Router System Board Layout

Primary Memory

DRAM SIMM

Ethernet

Serial

Console

AUX

Shared Memory

Fixed DRAM

System Code

Flash or PROM

Flash Card

Slot

Boot

ROMS

Polarization

Notch

Memory Types:


RAM/DRAM


NVRAM


Flash Memory


ROM

IIUSA


Internet Institute

Typical Cisco Motherboard for a 2500 Series

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Internet Institute

Sources For Configuring

Console Port

Auxiliary Port

Interfaces

VTY 0
-

4

TFTP Server

Dial
-
in Access with modems

Network

Management

Station

IIUSA


Internet Institute

Router and Switch Configuration