1. CIS 81 Fundamentals of Networking Chapter 7: IP Addressing Part 1 – IPv4
CCNA Introduction to Networking 5.0
Rick Graziani
Cabrillo College
Fall 2015

2. Number Systems and the Binary Number System

3. IPv4 Addresses IPv4 Addresses are 32 bit addresses:
We use dotted notation (or dotted decimal notation) to represent the value of each byte (octet) of the IP address in decimal.

4. IPv4 Addresses What are the range of addresses? …

5. Base 10 (Decimal) Number System
Digits (10): 0, 1, 2, 3, 4, 5, 6, 7, 8, 9
Number of:
10,000’s 1,000’s 100’s 10’s 1’s 1,

6. Number System Rules 1. All digits start with 0
2. A Base-n number system has n number of digits:
Decimal: Base-10 has 10 digits
Binary: Base-2 has 2 digits
Hexadecimal: Base-16 has 16 digits
3. The first column is always the number of 1’s
Each of the following columns is n times the previous column (n = Base-n)
Base 10: 10, ,
Base 2:
Base 16: 65, ,

7. Digits (2): 0, 1
Number of:
27 ___ ___ ___
128’s ’s 4’s 2’s 1’s
Dec. 17 70
130
255

8. Digits (2): 0, 1
Number of:
128’s 64’s 32’s 16’s 8’s 4’s 2’s 1’s
Dec.

9. Digits (2): 0, 1
Number of:
128’s 64’s 32’s 16’s 8’s 4’s 2’s 1’s
Dec.
172
192

10. Digits (2): 0, 1
Number of:
128’s 64’s 32’s 16’s 8’s 4’s 2’s 1’s
Dec.

11. IP Addressing Structure
We look at IP addresses using the “dotted decimal format” but network devices only understand the binary format.

12. Dotted Decimal Format

13. Decimal to Binary Assignment

14. Subnet Mask

15. Subnet Masks
An IP address is a hierarchical address that is made up of two parts:
A network portion
A host portion.
Subnet Mask
Used to define the:
Network portion
Host portion
32 bits
Contiguous set of 1’s followed by a contiguous set of 0’s
1’s: Network portion
0’s: Host portion

16. Dividing the Network and Host Portions
Dotted decimal:
Slash notation: /16
Expressed as:
Dotted decimal
Ex:
Slash notation or prefix length
/16 (the number of one bits)

17. Hierarchical Network Addressing
The IPv4 address with a subnet mask identifies:
The network portion
The host portion
C:\Users\Admin> ipconfig
Windows IP Configuration
Ethernet adapter Local Area Connection:
Connection-specific DNS Suffix . : cambrian.cambrianc.on.ca
Link-local IPv6 Address : fe80::b572:c6c:f983:cadc%11
IPv4 Address :
Subnet Mask :
Default Gateway :
C:\Users\Admin>

18. Subnet Mask:
192
168 11 10
255
255
255
The subnet mask identifies which part of the IP address refers to the network.
Network Portion
Host Portion
192
168 11
The prefix length is the number of bits set to 1 in the subnet mask.
It is written in “slash notation”, a “/” followed by the number of bits set to 1.
For example:
IP address:
Is the same as: /24

19. Valid Subnet Mask Values
128 64 32 16 8 4 2 1
Decimal Value 1
128 1 1
192 1 1 1
224 1 1 1 1
240 1 1 1 1 1
248 1 1 1 1 1 1
252 1 1 1 1 1 1 1
254 1 1 1 1 1 1 1 1
255

20. Subnet Masks
So how do hosts figure out which part of the address is the network portion?
Hosts AND the IPv4 address and the subnet mask.
“1” bits refer to the network portion.
“0” bits refer to the host portion.
Hosts actually use a the Boolean “AND” operation to accomplish this task.
This tells them what network they belong to.

21. Boolean AND Rules 1 “ANDed” with 1 = 1 0 “ANDed” with 1 = 0
/24
0 “ANDed” with anything = 0
IP Address
Network Portion
Subnet Mask 1 10
168
192
192
168 10

22. IPv4 AND Subnet Mask >> Network Address

23. A B
Source IPv4
Destination IPv4
How does the host know if the destination IPv4 address is on it’s network or another network?

24. Destination MAC Address?
Same network?
Same Network: Destination IP Address’s MAC Address
Different Network: The Default Gateway’s MAC Address
The Destination MAC Address will always be one of two addresses.
Same network: The MAC address associated with the device’s Destination IP Address.
Different network: The MAC address associated with the IP Address of the Default Gateway.

25. Destination MAC Address?
Same network?
So, here is the big question:
How do does the sending host know if the Source IP Address and Destination IP Address are on the same network?

26. Destination MAC Address?
Same network?
AND
AND
My Network =
Destination Network =
Same network? YES!

27. Destination MAC Address?
Same network
PC-A’s ARP Cache
IPv4 Address MAC Address
Check ARP Cache for the destination IPv4 address and a MAC address.
Not there? ARP Request

28. Destination MAC Address?
Same network?
Same Network: Destination IP Address’s MAC Address
Different Network: The Default Gateway’s MAC Address
The Destination MAC Address will always be one of two addresses.
Same network: The MAC address associated with the device’s Destination IP Address.
Different network: The MAC address associated with the IP Address of the Default Gateway.

29. Review: Destination MAC Address?
Same network?
AND
AND
My Network =
Destination Network =
Same network? NO!

30. Review: Destination MAC Address?
Different networks
PC-A’s ARP Cache
IPv4 Address MAC Address
Different Network: Need the Default Gateway’s MAC Address
Check ARP Cache for IPv4 address of the default gateway and a MAC address.
Not there? ARP Request

31. I only know what I know

32. Types of Addresses in a Network
/24
/24
/24
 Network Address
 Host Address
 Broadcast Address

33. Network Address /24
All devices in the network have the same network bits.
The network address has all 0 bits in the host portion.

34. Broadcast Address /24
A broadcast address is used to send data to all hosts in the network.
The broadcast address has all 1 bits in the host portion.

36. Bringing it all together
Convert these addresses and masks to Binary (to be used later)
Network:
Mask:
Broadcast Address
Network:
Mask:

37. Bringing it all together
Convert these addresses and masks to Binary (to be used later)
Network:
Mask:
Bcst:
Network:
Mask:
Bcst:
Bcst:

38. Bringing it all together
Convert these addresses and masks to Binary (to be used later)
Network:
Mask: /
Bcast:
Network:
Mask: /
Bst:
Network
Bcast

39. Host Address /24
In IPv4 addresses, host addresses are the addresses between the network address and the broadcast address devices in that network.
The host address does not have all 0 bits or all 1 bits in the host portion.
It is important to identify the first host address and the last host address.
Hosts within a network can be assigned IP addresses within this range.

40. 1st Host Address
The host portion of the first host address will contain all 0 bits with a 1 bit for the lowest order or right-most bit. (“All 0’s and a 1.”)
This address is always one greater than the network address.
For example the first host address is /24.
NOTE:
It is common in many addressing schemes to use the first host address for the router or default gateway address.

41. Last Host Address
The host portion of the last host address will contain all 1 bits with a 0 bit for the lowest order or right-most bit. (“All 1’s and a 0.”)
This address is always one less than the broadcast address.
For example, the last host address is

43. Range of hosts – Your Turn!
Host Addresses in binary
(net)
(SM)
(broadcast)
(net)
(SM)

44. Range of hosts – Your Turn!
Host Addresses in binary
(net)
(SM)
(broadcast)
(net)
(SM)

45. Range of hosts – Your Turn!
Host Addresses in binary
(net)
(SM)
(broadcast)

46. Range of hosts – The rest…
Host Addresses in binary
(net)
/24 (SM)
(broadcast)
(net)
/16 (SM)

47. Range of hosts – The rest…
Host Addresses in binary
(net)
/16 (SM)
(broadcast)

48. Subnet Masks: Non-Natural Boundaries
Subnet masks do not have to end on natural octet boundaries …
(broadcast)
Number of hosts: 212 – 2 = 4,096 – 2 = 4,094 hosts

49. Non-natural boundary masks
Host Addresses in binary
(net)
/20 (SM)
(broadcast)
(net)
/28 (SM)

50. Practice!

51. Addresses for User Devices

52. Addresses for User Devices
Hosts are assigned IP addresses from the range of available addresses in the network.
These IP addresses can be assigned either:
Statically
Dynamically

53. Static Assignment
Useful for printers, servers, and other networking devices that do not change location often and need to be accessible to clients on the network based on a fixed IP address.
Increased control of network resources.
However, static addressing can be time-consuming to enter on each host.

54. Dynamic Assignment
Instead of manually assigning IP addresses (subnet mask, default gateway, DNS addresses), it is easier to have IP addresses assigned automatically.
This is done using Dynamic Host Configuration Protocol (DHCP).
The DHCP server requires that a block of addresses, called an address pool, is used for assigning to the DHCP clients on a network.

55. How Does DHCP Work? A DHCP Server must be available.
It must have a pre-configured range (scope) of IP addresses.
As clients come online they contact the DHCP server and request an address.
The DHCP server chooses an address and allocates it to that host.

56. DHCP Server Scope

57. How Does DHCP Work? Client Boots DHCP Discover DHCP Request DHCP Offer
Mac Address
DHCP Request
IP, MAC Address
Client
DHCP Server
DHCP Offer
IP, Lease time
DHCP Ack
IP, Lease time

58. Dynamic Addressing 58

59. Dynamic vs. Static IP Addressing Quiz
Desktop computer
Server
Router
Switch
Laptop
IP phone
Printer
RADIUS server AP
PDA
iTouch
Fridge
Static IP Address
Dynamic (DHCP) IP Address

60. Unicast, Multicast, and Broadcast

61. Destination Unicasts, Multicasts, and Broadcasts
Source IP addresses are always unicast
Unicasts:
Packet travels from one host to another specific host.
Multicasts:
Packet travels from one host to a select number of other hosts.
Supports voice and audio broadcasts, news feeds, distribution of software, re-imaging clients off peak times.
Broadcasts:
Packet travels from one host to all hosts on the local network.

62. Unicast Addresses 62

63. Multicast Addresses For example:
One hosts sends packets to the multicast IP address /24.
Multicast clients subscribe to the multicast group and listen for packets destined to 63

64. Broadcast Addresses
Directed broadcast is sent to all hosts on a specific network. An example destination IPv4 address is /24.
Limited broadcast is to all hosts on the local network. These packets use a destination IPv4 address 64

65. Private vs. Public Addresses

66. Private Addresses Most IPv4 addresses are public IP addresses.
These are reachable IPv4 addresses on the Internet.
However, there are blocks of addresses that are private addresses and are never propagated on the Internet.
Packets with a source or destination private IP address are not propagated by Internet routers.
Internet routers / firewalls block or translate these addresses.
Private addresses are usually converted to public IP addresses using NAT (Network Address Translation)

67. Private Addresses Private addresses are defined in RFC 1918.
The private address blocks are:
/8: to
/12: to
/16: to
RFC 6598, IANA reserved /10 known as shared address space.
Similar to RFC 1918, but intended only for use in service provider networks.

68. Other Special Addresses
Refer to RFC 3330
Loopback address: –
Hosts use to direct traffic to themselves.
Link-Local addresses: /16 –
Host can automatically assign itself an address if it has none.
TEST-NET addresses:
to ( /24) 68

69. Special Addresses TEST-NET Addresses
to ( /24)
The address block is set aside for teaching and learning purposes and are sometimes used in documentation and network examples.
You may often find these addresses used with the domain names example.com or example.net in RFCs, vendor, and protocol documentation.
Addresses within this block should not appear on the Internet. 69

70. How addressing space use to be assigned.
Classful Addressing
How addressing space use to be assigned.
Historically, RFC1700 grouped the unicast ranges into specific sizes referred to as Classful addressing for IPv4 (never existed for IPv6):
Class A, B, and C addresses:
Multicast addresses:
Experimental addresses: 70

71. IPv4 Address Classes
Class A /8
Class B /16
Class C /24

72. Total Possible Addresses
IPv4 Address Classes
Address Class
# of Possible Networks
# of Possible Hosts
Total Possible Addresses
Class A
Class B
Class C
126
16,777,214
532,676,608
1,073,709,056
2,113,928,964
16,384
65,534
2,097,152
254
Class A or /8
Was reserved for governments and extremely large organizations.
Class B or /8
Was reserved for medium/large organizations.
Class C or /24
Was for every other organization (small organizations).

73. How the ranges were determined
First First Network Host
Class Bits Octet Bits Bits
A – B C
D – 239 E

74. Fill in the information…
Class C Default Mask:
Network: Broadcast:
Hosts: through
Class A Default Mask:
Network: Broadcast:
Hosts: through
Class B Default Mask:
Network: Broadcast:
Hosts: through

75. Class separates network from host bits
The Class determines the Base Network Mask!
Class C Default Mask:
Network:
Class A Default Mask:
Network:
Class B Default Mask:
Network:

76. Total Possible Addresses
IP Address Allocation
Initially, IP addresses were allocated to organizations based on request rather than need.
Address Class
# of Possible Networks
# of Possible Hosts
Total Possible Addresses
Class A
Class B
Class C
126
16,777,214
532,676,608
1,073,709,056
2,113,928,964
16,384
65,534
2,097,152
254

77. IP Address Allocation – Visual Perspective
Class A
Total Nets: 126
Total Hosts/Net: 16,777,214
Class C
Total Nets: 2,097,152
Total Hosts/Net: 254
The Internet is now based on a Classless addressing scheme.
NOTE:
Class B
Total Nets: 16,384
Total Hosts/Net: 65,534

78. /8 ( ) 16,777,216 host addresses
/9 ( ) 8,388,608 host addresses
/10 ( ) 4,194,304 host addresses
/11 ( ) 2,097,152 host addresses
/12 ( ) 1,048,576 host addresses
/13 ( ) 524,288 host addresses
/14 ( ) 262,144 host addresses
/15 ( ) 131,072 host addresses
/16 ( ) 65,536 host addresses
/17 ( ) 32,768 host addresses
/18 ( ) 16,384 host addresses
/19 ( ) 8,192 host addresses
/20 ( ) 4,096 host addresses
/21 ( ) 2,048 host addresses
/22 ( ) 1,024 host addresses
/23 ( ) 512 host addresses
/24 ( ) 256 host addresses
/25 ( ) 128 host addresses
/26 ( ) 64 host addresses
/27 ( ) 32 host addresses
/28 ( ) 16 host addresses
/29 ( ) 8 host addresses
/30 ( ) 4 host addresses
/31 ( ) 2 host addresses
/32 ( ) “Host Route”
ISPs no longer restricted to three classes. Can now allocate a large range of network addresses based on customer requirements

79. Public Addresses

80. Public Addresses
Public addresses are required on the Internet and they must be unique.
The use of public addresses is regulated and allocated to each organization separately.
RIRs (Regional Internet Registries) typically provide public addresses to ISPs.
Companies obtain their IPv4 address blocks from an ISP.
In a sense, the ISP loans or rents these addresses to the organization.

81. RIRs
These registration companies are called Regional Internet Registries (RIRs).
IANA
ARIN
(American Registry for Internet Numbers)
North America Region
RIPE NCC (Reseaux IP Europeans)
Europe, the Middle East, and Central Asia
APNIC
(Asia Pacific Network Information Centre)
Asia/Pacific Region
AfriNIC
(African Network Information Centre)
Africa Region
LACNIC
(Regional Latin-American and Caribbean IP Address Registry)
Latin America and some Caribbean Islands

82. The 3 Tiers of ISP
ISPs are designated by a hierarchy based on their level of connectivity to the Internet backbone.
Each lower tier obtains connectivity to the backbone via a connection to a higher tier ISP.
The Internet backbone is built on a three tier hierarchy.
Tier 1 = AT&T, Verizon (UUNET), SAVVIS, Sprintlink, Bell, Level 3 Networks, Qwest, …
Tier 2 = Cogent, Eastlink, Orion, Canarie, nLayer, France Télécom, …
Tier 3 = Local ISPs

83. The 3 Tiers of ISPs RIR ARIN Tier 1 Sprint SAVVIS … Tier 2 Tier 3
Tiers 1 ISPs have multiple, direct connections to the Internet backbone.
Primarily serves very large companies and Tier 2 ISPs.
Sprint
SAVVIS …
Connect to the Internet via Tier 1 ISPs.
Primarily serves large companies and Tier 3 ISPs.
Tier 2
nLayer
Cogent …
Connect to the Internet via Tier 2 ISPs.
Primarily serves homes, and small to medium companies.
Tier 3
Fortress ITX
Beachcomputers …

87. CIS 81 Fundamentals of Networking IP Addressing Part 1 – IPv4
CCNA Introduction to Networking 5.0
Rick Graziani
Cabrillo College