1. IPv4 and Subnetting
Part 1

2. Announcements and Outline
IPv4
Review of packet formats and addressing
Assigning Addresses
Public vs. Private
Dotted decimal notation 2

3. IP Packet Formats IPv4 Header: 192 bits (24 bytes)

4. IPv6 Addressing IPv4 uses 4 byte addresses:
Total of 4 billion possible addresses
IP addresses often assigned in (large) groups
Giving out many numbers at a time
 IPv4 address space has been used up quickly
IPv6 uses 16 byte addresses:
3.2 x 1038 addresses, 320 undecillion
Little chance this address space will ever be used up

5. Types of Addresses Application Layer Address Network Layer Address
Data Link Layer Address
Application Layer
Transport Layer
Network Layer
Data Link Layer

6. Assigning Addresses

7. IP Addressing Structure
The dotted decimal structure of a binary IP address and label its parts

8. IP Addressing Structure
The general role of 8-bit binary in network addressing and convert 8-bit binary to decimal

9. IPv4 Addresses 4 byte (32 bit) addresses Dotted decimal notation
Strings of 32 binary bits
Dotted decimal notation
Used to make IP addresses easier to understand for human readers
Breaks the address into four bytes and writes the digital equivalent for each byte
Example:

10. IP Addresses (dotted decimal notation)
Examples

11. Binary and Decimal Conversion

12. Converting from binary to decimal
Use the same template as before
Add the place values corresponding to the locations that have 1 in the number
E.g.:
128
(2^7) 64
(2^6) 32
(2^5) 16
(2^4) 8
(2^3) 4
(2^2) 2
(2^1) 1
(2^0)
In decimal, this number is:

13. Converting from binary to decimal
You should be comfortable working with binary numbers with up to 8 bits
e.g.:
128 64 32 16 8 4 2 1
This number is equal to:
Largest possible number with 8 digits?

14. Converting from binary to decimal
Try converting the following numbers to decimal
128 64 32 16 8 4 2 1
128 64 32 16 8 4 2 1

15. IPv4 – Binary to Dotted Decimal Notation

16. Converting from decimal to binary
Used to compute subnet sizes, broadcast addresses etc.
You should be comfortable with binary numbers with up to 8 digits
One technique is to fill-in-the-blanks
Start with template below
Place 1 in the leftmost-possible position
Subtract place-value and repeat until subtraction yields 0
128 64 32 16 8 4 2 1

17. Converting from decimal to binary
e.g.: 133
128 64 32 16 8 4 2 1
128 64 32 16 8 4 2 1

18. Converting from decimal to binary
Try converting the following numbers to binary
134
200
240

19. IP addresses – structure
IP addresses are not assigned at random like MAC addresses
Or even on first-come-first-serve basis
The first few address bits define the organization to which the address belongs
Remaining bits are unique to the computer (host) within the organization

20. Assigning Addresses - Network Classes (IPv4)

21. Class A networks

22. Class B and C networks
Class B networks Class C networks

23. Public and Private IP Addresses
The use of these addresses need not be unique among outside networks. Hosts that do not require access to the Internet at large may make unrestricted use of private addresses.
The private address blocks are:
to ( /8)
to ( /12)
to ( /16)
Does UNCW use the private address blocks within their network?

24. Introducing NAT and PAT
NAT is designed to conserve IP addresses and enable networks to use private IP addresses on internal networks.
These private, internal addresses are translated to routable, public addresses.
IPv4 addresses are almost depleted.
NAT/PAT has allowed IPv4 to be the predominant network protocol
With services to translate private addresses to public addresses, hosts on a privately addressed network can have access to resources across the Internet. These services, called Network Address Translation (NAT), can be implemented on a device at the edge of the private network.
NAT allows the hosts in the network to "borrow" a public address for communicating to outside networks. While there are some limitations and performance issues with NAT, clients for most applications can access services over the Internet without noticeable problems.
Note: NAT will be covered in detail in a subsequent course.

25. When should you use public / private addresses?