IPv4 and Subnetting Part 1

Announcements and Outline Review assignment due on Weds. Assessment 2 – next Monday, 2/27 Exercise 5 due next Weds., 3/1 IPv4 Review of packet formats and addressing Assigning Addresses Public vs. Private Dotted decimal notation 2

IP Packet Formats IPv4 Header: 192 bits (24 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

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

Assigning Addresses

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

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 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: 128.192.56.1 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

Binary and Decimal Conversion

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.: 11100011 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:

Converting from binary to decimal You should be comfortable working with binary numbers with up to 8 bits e.g.: 10011011 128 64 32 16 8 4 2 1 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 128 64 32 16 8 4 2 1 10000110 =>134 11001000 => 200 11110000 => 240 128 64 32 16 8 4 2 1

IPv4 – Binary to Dotted Decimal Notation

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

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

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

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

Assigning Addresses - Network Classes (IPv4) https://www.arin.net/knowledge/address_filters.html

Class A networks

Class B and C networks Class B networks Class C networks

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?

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.

When should you use public / private addresses?