1 08 Peter J. Smith. All rights reserved. Addressing the Network – IPv4 Network Fundamentals – Chapter 6 A Compiled by Peter J. Smith
Nov 15, 2014
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Addressing the Network – IPv4
Network Fundamentals – Chapter 6 A
Compiled by Peter J. Smith
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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
TCP/IP model Internet layer
Application
Presentation
Session
Transport
Network
Data link
Physical
Application
Transport
Internet
Network Access
TCP, UDP
IP
Ethernet, WAN technologies
HTTP, FTP, TFTP, SMTP etc
Segment
Packet
Frame
Bits
Data stream
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Addressing topics
Binary and decimal
Types of IP addresses
Assigning addresses
Network part and subnet masks
Calculating addresses
Ping and Traceroute Utilities
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Binary and decimal
Convert to 8-bit binary
248
187
89
Convert to decimal
00110100
01010101
11001111
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248 to binary
128 64 32 16 8 4 2 1
1 1 1 1 1 0 0 0
248-128120
24-16
8
56-3224
120-6456
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187 to binary
128 64 32 16 8 4 2 1
1 0 1 1 1 0 1 1
187-128
59
27-1611
11-83
59-3227
3-21
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89 to binary
128 64 32 16 8 4 2 1
0 1 0 1 1 0 0 1
89-6425
25-16
9
9-81
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00110100 to decimal
128 64 32 16 8 4 2 1
0 0 1 1 0 1 0 0
32 16 4
32 +16+ 452
52
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01010101 to decimal
128 64 32 16 8 4 2 1
0 1 0 1 0 1 0 1
64 16 4 1
64 +16+ 4+ 185
85
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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+ 1207
207
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Binary and decimal
Convert to 8-bit binary
248 11111000
187 10111011
89 01011001
Convert to decimal
00110100 52
01010101 85
11001111 207
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IPv4 address
192. 168. 21. 17
11000000 10101000 00010101 00010001
octetoctet octet octet
network part host part
255. 255. 255. 0
11111111 11111111 11111111 00000000
Prefix /24 Subnet mask:
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Find the network address
192. 168. 21. 17
11000000 10101000 00010101 00010001
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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Logical AND
192. 168. 21. 17
11000000 10101000 00010101 00010001
255. 255. 255. 0
11111111 11111111 11111111 00000000
Do a logical AND at each position
192. 168. 21. 0
11000000 10101000 00010101 00000000
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Find the broadcast address
192. 168. 21. 17
11000000 10101000 00010101 00010001
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
Host addresses – everything in between
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Classful addressing
10. 17. 53. 60
network part host part
A
172. 16. 38. 201
network part host part
B
192. 168. 21. 17
network part host part
C
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Classful addressing
Easy to work out but very wasteful.
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.
More flexible, less wasteful.
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Classless addressing /16
172.16.0.0/16 mask 255.255.0.0
Broadcast address 172.16.255.255
Hosts 172.16.0.1 to 172.16.255.254
65534 host addresses
172. 16. 0. 0
10101100 00010000 00000000 00000000
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Classless addressing /24
172.16.0.0/24 mask 255.255.255.0
Broadcast address 172.16.0.255
Hosts 172.16.0.1 to 172.16.0.254
254 host addresses
172. 16. 0. 0
10101100 00010000 00000000 00000000
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Classless addressing /22
172.16.0.0/22 mask 255.255.252.0
Broadcast address 172.16.3.255
Hosts 172.16.0.1 to 172.16.3.254
1022 host addresses
172. 16. 0. 0
10101100 00010000 00000000 00000000
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Classless addressing /26
172.16.0.0/22 mask 255.255.255.192
Broadcast address 172.16.0.63
Hosts 172.16.0.1 to 172.16.0.62
62 host addresses
172. 16. 0. 0
10101100 00010000 00000000 00000000
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Classless addressing /28
172.16.0.0/28 mask 255.255.255.240
Broadcast address 172.16.0.15
Hosts 172.16.0.1 to 172.16.0.14
14 host addresses
172. 16. 0. 0
10101100 00010000 00000000 00000000
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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?
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
Network
Broadcast
First host
Last host
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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 255 192.168.1.255
First host 00000001 1 192.168.1.1
Last host 11111110 254 192.168.1.254
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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?
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
Network
Broadcast
First host
Last host
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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
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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?
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
Network
Broadcast
First host
Last host
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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
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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
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)
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
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.
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.
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
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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Blocks of addressesUse 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
Address 192.168.1.0 00000000
Subnet mask 255.255.255.0 00000000
Last octet binary
Borrow 1 bit from host part, give it to network part, /25
Addresses 192.168.1.0192.168.1.128
0000000010000000
Subnet mask 255.255.255.128 10000000
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Subnetting 192.168.1.0/24
Borrow 2 bits from host part, give to network part, /26
Addresses 192.168.1.0192.168.1.64192.168.1.128192.168.1.192
00000000010000001000000011000000
Subnet mask 255.255.255.192 11000000
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Subnetting 192.168.1.0/24
Borrow 3 bits from host part, give to network part, /27
Addresses 192.168.1.0192.168.1.32192.168.1.64192.168.1.96192.168.1.128 192.168.1.160 192.168.1.192 192.168.1.224
0000000000100000010000000110000010000000101000001100000011100000
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, /28192.168.1.0192.168.1.16192.168.1.32192.168.1.48192.168.1.64192.168.1.80192.168.1.96192.168.1.112
192.168.1.128192.168.1.144192.168.1.160192.168.1.176 192.168.1.192192.168.1.208192.168.1.224192.168.1.240
0000000000010000001000000011000001000000010100000110000001110000
1000000010010000 1010000010110000 1100000011010000 1110000011110000
Subnet mask 255.255.255.240 11110000
And so on…
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Subnetting 192.168.1.0/24
Every time you borrow another bit you:
Double the number of subnets
Halve the size of the subnets
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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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
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Address space
Make a spreadsheet or table with numbers 0 to 255
Link to show table
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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.
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.
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
Simpler header
Integrated security – authentication, privacy
Quality of service mechanisms
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Summary
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