Part 1

IPv4 and Subnetting

Announcements and OutlineAssessment 1 Results:Range: 66 – 112Average: 859 students did extra credit

Curve3 MC Questions (6 pts)3pts on Essay Questions

IPv4• Review of packet formats and addressing• Assigning Addresses

• Public vs. Private

• Dotted decimal notation

2

D D+ C- C C+ B- B B+ A- A0

1

2

3

4

5

6

7

IP Packet Formats

5 - 3

IPv4 Header: 192 bits (24 bytes)

IPv6 Header: 320 bits (40 bytes)

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 - 4

Types of Addresses

5 - 5

• Application Layer Address

• Network Layer Address

• Data Link Layer Address

Network Layer

Data Link Layer

Application Layer

Transport Layer

Assigning Addresses

5 - 6

7© 2007 Cisco Systems, Inc. All rights reserved. Cisco Public

IP Addressing Structure The dotted decimal structure of a binary IP address and

label its parts

8© 2007 Cisco Systems, Inc. All rights reserved. Cisco Public

IP Addressing Structure The general role of 8-bit binary in network addressing

and convert 8-bit binary to decimal

6.1.1.1

IPv4 Addresses

4 byte (32 bit) addresses 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: 128.192.56.1

5 - 9

1 0 0 0 0 0 0 0 1 1 0 0 0 0 0 0 0 0 1 1 1 0 0 0 0 0 0 0 0 0 0 1

IP Addresses (dotted decimal notation)

Examples

10

11000000 10101000 00000001 00000101

192 . 168 . 1 5

Binary and Decimal Conversion

5 - 11

Converting from binary to decimal

128(2^7)

64(2^6)

32(2^5)

16(2^4)

8(2^3)

4(2^2)

2(2^1)

1 (2^0)

12

In decimal, this number is:

• Use the same template as before• Add the place values corresponding to the

locations that have 1 in the number• E.g.: 11100011

Converting from binary to decimal

128 64 32 16 8 4 2 1

13

You should be comfortable working with binary numbers with up to 8 bits e.g.: 10011011

• This number is equal to:

• Largest possible number with 8 digits?

Converting from binary to decimal

Try converting the following numbers to decimal 10000110

11001000

11110000

14

128 64 32 16 8 4 2 1

128 64 32 16 8 4 2 1

IPv4 – Binary to Dotted Decimal Notation

5 - 15

Converting from decimal to binary

128 64 32 16 8 4 2 1

16

• 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

Converting from decimal to binary

128 64 32 16 8 4 2 1

17

e.g.: 133

128 64 32 16 8 4 2 1

Converting from decimal to binary

Try converting the following numbers to binary 134

200

240

18

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

19

Assigning Addresses - Network Classes (IPv4)

5 - 20

https://www.arin.net/knowledge/address_filters.html

Class A networks

21

Class B and C networksClass B networks

Class C networks

22

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:• 10.0.0.0 to 10.255.255.255 (10.0.0.0 /8)• 172.16.0.0 to 172.31.255.255 (172.16.0.0 /12)• 192.168.0.0 to 192.168.255.255 (192.168.0.0 /16)

Does UNCW use the private address blocks within their network?

5 - 23

24© 2007 Cisco Systems, Inc. All rights reserved. Cisco Public

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

When should you use public / private addresses?

5 - 25