Addressing The Network - Ipv4 And Subnetworking (ip Adressing And Subnetting)

© 2008 Peter J. Smith. All rights reserved.

Addressing the Network – IPv4

Network Fundamentals – Chapter 6 A Compiled by Peter J. Smith

1

© 2008 Peter J. Smith. All rights reserved.

Objectives 

Explain the structure IP addressing and demonstrate the ability to convert between 8-bit binary and decimal numbers.



Given an IPv4 address, classify by type and describe how it is used in the network



Explain how addresses are assigned to networks by ISPs and within networks by administrators



Determine the network portion of the host address and explain the role of the subnet mask in dividing networks.



Given IPv4 addressing information and design criteria, calculate the appropriate addressing components.



Use common testing utilities to verify and test network connectivity and operational status of the IP protocol stack on a host.

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IP addressing – works at  OSI model layer 3

© 2008 Peter J. Smith. All rights reserved.

 TCP/IP model Internet layer Application Presentation Session Transport Network Data link Physical

Data stream

HTTP, FTP, TFTP, SMTP etc

Segment

TCP, UDP

Packet

IP

Frame

Ethernet, WAN technologies

Bits

Application Transport Internet Network Access

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Addressing topics  Binary and decimal  Types of IP addresses  Assigning addresses  Network part and subnet masks © 2008 Peter J. Smith. All rights reserved.

 Calculating addresses  Ping and Traceroute Utilities

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Binary and decimal  Convert to 8-bit binary  248  187  89 © 2008 Peter J. Smith. All rights reserved.

 Convert to decimal  00110100  01010101  11001111 5

© 2008 Peter J. Smith. All rights reserved.

248 to binary 128

64

32

16

8

4

2

1

1

1

1

1

1

0

0

0

248 -128 120

120 -64 56

56 -32 24

24 -16 8

6

© 2008 Peter J. Smith. All rights reserved.

187 to binary 128

64

32

16

8

4

2

1

1

0

1

1

1

0

1

1

59 -32 27

27 -16 11

187 -128 59

11 -8 3

3 -2 1

7

© 2008 Peter J. Smith. All rights reserved.

89 to binary 128

64

32

16

8

4

2

1

0

1

0

1

1

0

0

1

89 -64 25

25 -16 9

9 -8 1

8

© 2008 Peter J. Smith. All rights reserved.

00110100 to decimal 128

64

32

16

8

4

2

1

0

0

1

1

0

1

0

0

32

16

32 +16 + 4 52

4

52

9

01010101 to decimal 128

64

32

16

8

4

2

1

0

1

0

1

0

1

0

1

© 2008 Peter J. Smith. All rights reserved.

64

64 +16 + 4 + 1 85

16

4

1

85

10

© 2008 Peter J. Smith. All rights reserved.

11001111 to decimal 128

64

32

16

8

4

2

1

1

1

0

0

1

1

1

1

128

64

8

4

2

1

128 + 64 + 8 + 4 + 2 + 1 207

207

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Binary and decimal  Convert to 8-bit binary  248

11111000

 187

10111011

 89

01011001

© 2008 Peter J. Smith. All rights reserved.

 Convert to decimal  00110100

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 01010101

85

 11001111

207 12

IPv4 address 192.

168.

21.

17

11000000

10101000

00010101

00010001

octet

octet

octet

© 2008 Peter J. Smith. All rights reserved.

network part

octet host part

Prefix /24 Subnet mask: 255.

255.

255.

0

11111111

11111111

11111111

00000000

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Find the network address 192.

168.

21.

17

11000000

10101000

00010101

00010001

© 2008 Peter J. Smith. All rights reserved.

In a network address, all the host bits are 0. 192.

168.

21.

0

11000000

10101000

00010101

00000000

The router needs to do this for every packet.

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© 2008 Peter J. Smith. All rights reserved.

Logical AND 192.

168.

21.

17

11000000

10101000

00010101

00010001

255.

255.

255.

0

11111111

11111111

11111111

00000000

192.

168.

21.

0

11000000

10101000

00010101

00000000

Do a logical AND at each position 15

Find the broadcast address 192.

168.

21.

17

11000000

10101000

00010101

00010001

© 2008 Peter J. Smith. All rights reserved.

In a broadcast address, all the host bits are 1. 192.

168.

21.

255

11000000

10101000

00010101

11111111

The broadcast is the last address in the network.

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3 types of address  Every network has:  Network address – the first one  Broadcast address – the last one

© 2008 Peter J. Smith. All rights reserved.

 Host addresses – everything in between

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Classful addressing A

10.

17.

network part

B

172.

53.

host part 16.

38.

© 2008 Peter J. Smith. All rights reserved.

network part

C

192.

60

201

host part 168.

network part

21.

17

host part

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Classful addressing  Easy to work out but very wasteful.

© 2008 Peter J. Smith. All rights reserved.

 Routers and hosts still assume class subnet masks by default  Class A

/8

255.0.0.0

 Class B

/16

255.255.0.0

 Class C

/24

255.255.255.0

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Classless addressing  Any suitable prefix can be used  We (and devices) need to know what the prefix is.

© 2008 Peter J. Smith. All rights reserved.

 More flexible, less wasteful.

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Classless addressing /16  172.16.0.0/16 mask 255.255.0.0

© 2008 Peter J. Smith. All rights reserved.

 Broadcast address 172.16.255.255 172.

16.

0.

0

10101100

00010000

00000000

00000000

 Hosts 172.16.0.1 to 172.16.255.254  65534 host addresses

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Classless addressing /24  172.16.0.0/24 mask 255.255.255.0

© 2008 Peter J. Smith. All rights reserved.

 Broadcast address 172.16.0.255 172.

16.

0.

0

10101100

00010000

00000000

00000000

 Hosts 172.16.0.1 to 172.16.0.254  254 host addresses

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Classless addressing /22  172.16.0.0/22 mask 255.255.252.0

© 2008 Peter J. Smith. All rights reserved.

 Broadcast address 172.16.3.255 172.

16.

0.

0

10101100

00010000

00000000

00000000

 Hosts 172.16.0.1 to 172.16.3.254  1022 host addresses

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Classless addressing /26  172.16.0.0/22 mask 255.255.255.192

© 2008 Peter J. Smith. All rights reserved.

 Broadcast address 172.16.0.63 172.

16.

0.

0

10101100

00010000

00000000

00000000

 Hosts 172.16.0.1 to 172.16.0.62  62 host addresses

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Classless addressing /28  172.16.0.0/28 mask 255.255.255.240

© 2008 Peter J. Smith. All rights reserved.

 Broadcast address 172.16.0.15 172.

16.

0.

0

10101100

00010000

00000000

00000000

 Hosts 172.16.0.1 to 172.16.0.14  14 host addresses

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Calculating addresses  A host has IP address 192.168.1.70/24  What is the subnet mask?  What is the network address?  What is the broadcast address? © 2008 Peter J. Smith. All rights reserved.

 What is the range of host addresses in the network?

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192.168.1.70/24 – fill in the table Last octet binary

Last octet decimal

Full

Host Subnet mask

© 2008 Peter J. Smith. All rights reserved.

Network Broadcast First host Last host 27

© 2008 Peter J. Smith. All rights reserved.

192.168.1.70/24 Last octet binary

Last octet decimal

Full

Host

01000110

70

192.168.1.70

Subnet mask

00000000

0

255.255.255.0

Network

00000000

0

192.168.1.0

Broadcast

11111111

255

First host

00000001

1

Last host

11111110

254

192.168.1.255 192.168.1.1 192.168.1.254 28

Calculating addresses  A host has IP address 192.168.1.70/26  What is the subnet mask?  What is the network address?  What is the broadcast address? © 2008 Peter J. Smith. All rights reserved.

 What is the range of host addresses in the network?

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192.168.1.70/26 fill in the table Last octet binary

Last octet decimal

Full

Host Subnet mask

© 2008 Peter J. Smith. All rights reserved.

Network Broadcast First host Last host 30

© 2008 Peter J. Smith. All rights reserved.

192.168.1.70/26 Last octet binary

Last octet decimal

Full

Host

01000110

70

192.168.1.70

Subnet mask

11000000

192

255.255.255.192

Network

01000000

64

192.168.1.64

Broadcast

01111111

127

192.168.1.127

First host

01000001

65

192.168.1.65

Last host

01111110

126

192.168.1.126 31

Calculating addresses  A host has IP address 192.168.1.70/28  What is the subnet mask?  What is the network address?  What is the broadcast address? © 2008 Peter J. Smith. All rights reserved.

 What is the range of host addresses in the network?

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192.168.1.70/28 fill in the table Last octet binary

Last octet decimal

Full

Host Subnet mask

© 2008 Peter J. Smith. All rights reserved.

Network Broadcast First host Last host 33

© 2008 Peter J. Smith. All rights reserved.

192.168.1.70/28 Last octet binary

Last octet decimal

Full

Host

01000110

70

192.168.1.70

Subnet mask

11110000

240

255.255.255.240

Network

01000000

64

192.168.1.64

Broadcast

01001111

79

192.168.1.79

First host

01000001

65

192.168.1.65

Last host

01001110

78

192.168.1.78 34

Unicast, Multicast, Broadcast  Unicast – a message addressed to one host  Broadcast – a message addressed to all hosts on a network. Uses network’s broadcast address or 255.255.255.255 locally

© 2008 Peter J. Smith. All rights reserved.

 Multicast – a message addressed to a group of hosts. Uses an address starting 224 - 239

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Private IP addresses  Unrestricted use on private networks. Not routed across the Internet.  10.0.0.0 – 10.255.255.255 (10.0.0.0/8)  172.16.0.0 – 172.31.255.255 (172.16.0.0/20)

© 2008 Peter J. Smith. All rights reserved.

 192.168.0.0 – 192.168.255.255 (192.168.0.0/24)

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Public IP addresses  Routed over the Internet  Master holder is IANA  Assigned to regional registries and then to ISPs

© 2008 Peter J. Smith. All rights reserved.

 ISPs allocate them to organisations and individual users  Use is strictly controlled as duplicate addresses are not allowed

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Special addresses  0.0.0.0 “all addresses” in default route. Hosts cannot be given addresses starting 0.  127.0.0.1 is loopback. Hosts cannot be given addresses starting 127.

© 2008 Peter J. Smith. All rights reserved.

 240.0.0.0 and higher – reserved for experimental purposes.  169.254.0.0 - 169.254.255.255 local only  192.0.2.0 to 192.0.2.255 for teaching

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Network address translation  A large number of hosts on a network use private addresses to communicate with each other.  The ISP allocates one or a few public addresses.

© 2008 Peter J. Smith. All rights reserved.

 NAT allows the hosts to share the public addresses when they want to use the Internet

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Addressing hosts  Static addressing – address is configured by an administrator

© 2008 Peter J. Smith. All rights reserved.

 Servers, printers, routers, switches need static addresses  Dynamic addressing – address is allocated automatically by DHCP by leasing addresses from a pool  Dynamic addressing is best for workstations

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© 2008 Peter J. Smith. All rights reserved.

Blocks of addresses Use

Address range

Summary

Network address

192.168.1.0

192.168.1.0/25

User hosts

192.168.1.1-127

Servers

192.168.1.128 - 191

192.168.1.128/26

Peripherals

192.168.1.192 - 223

192.168.1.192/27

Network devices

192.168.1.224 - 253

192.168.1.224/27

Router

192.168.1.254

Broadcast

192.168.1.255

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Subnetting 192.168.1.0/24 Last octet binary Address

192.168.1.0

00000000

Subnet mask

255.255.255.0

00000000

© 2008 Peter J. Smith. All rights reserved.

Borrow 1 bit from host part, give it to network part, /25 Addresses

192.168.1.0 192.168.1.128

00000000 10000000

Subnet mask

255.255.255.128

10000000

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Subnetting 192.168.1.0/24

© 2008 Peter J. Smith. All rights reserved.

Borrow 2 bits from host part, give to network part, /26 Addresses

192.168.1.0 192.168.1.64 192.168.1.128 192.168.1.192

00000000 01000000 10000000 11000000

Subnet mask

255.255.255.192

11000000

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Subnetting 192.168.1.0/24

© 2008 Peter J. Smith. All rights reserved.

Borrow 3 bits from host part, give to network part, /27 Addresses

192.168.1.0 192.168.1.32 192.168.1.64 192.168.1.96 192.168.1.128 192.168.1.160 192.168.1.192 192.168.1.224

00000000 00100000 01000000 01100000 10000000 10100000 11000000 11100000

Subnet mask

255.255.255.224

11100000

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Subnetting 192.168.1.0/24 Borrow 4 bits from host part, give to network part, /28

© 2008 Peter J. Smith. All rights reserved.

192.168.1.0 192.168.1.16 192.168.1.32 192.168.1.48 192.168.1.64 192.168.1.80 192.168.1.96 192.168.1.112

192.168.1.128 192.168.1.144 192.168.1.160 192.168.1.176 192.168.1.192 192.168.1.208 192.168.1.224 192.168.1.240

Subnet mask 255.255.255.240

00000000 00010000 00100000 00110000 01000000 01010000 01100000 01110000

10000000 10010000 10100000 10110000 11000000 11010000 11100000 11110000

11110000

And so on… 45

Subnetting 192.168.1.0/24  Every time you borrow another bit you: Double the number of subnets Halve the size of the subnets

© 2008 Peter J. Smith. All rights reserved.

 Each subnet has a network address, a broadcast address, and everything in between is a host address.  Here are some ways of visualising the process.

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© 2008 Peter J. Smith. All rights reserved.

Subnetting 192.168.1.0/24 Bits borrowed

1

2

3

4

5

6

No of networks

2

4

8

16

32

64

Prefix

/25

/26

/27

/28

/29

/30

Bit value/ network size

128

64

32

16

8

4

No of hosts

126

62

30

14

6

2

Subnet mask

128

192

224

240

248

252

47

Address space  Make a spreadsheet or table with numbers 0 to 255

© 2008 Peter J. Smith. All rights reserved.

 Link to show table

48

© 2008 Peter J. Smith. All rights reserved.

Subnet chart

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Subnetting  There are many subnet calculators, but you will not be able to use them in exams.  Start with the biggest subnet and work down to the smallest.

© 2008 Peter J. Smith. All rights reserved.

 Make sure the subnets are valid sizes with valid subnet masks.  Make sure that there are no overlaps.

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Ping and traceroute  Ping sends an ICMP message. If all is well, the destination replies. If not, a router may reply to say the destination is unreachable, or the ping may time out.

© 2008 Peter J. Smith. All rights reserved.

 Traceroute sends a series of messages so that each router along the path replies. You get a list of addresses of all the routers.

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IPv6  Development started in 1990s because of concerns about IPv4 addresses running out  A whole new protocol suite – not just layer 3  Uses 128-bit hierarchical addressing, written using hexadecimal © 2008 Peter J. Smith. All rights reserved.

 Simpler header  Integrated security – authentication, privacy  Quality of service mechanisms

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© 2008 Peter J. Smith. All rights reserved.

Summary

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© 2008 Peter J. Smith. All rights reserved.

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