IPv4 vs IPv6: Addressing and Network Identifiers

• IP has undergone several version changes
• There are two IP versions, IPv4 and IPv6

IP version 4 (IPv4)

• Deployed in 1981
• Uses a 32-bit (4 bytes) addressing scheme
• Address format is Dotted Decimal Notation, like 192.149.252.76
• Prefix Notation example: 192.149.0.0/24
• Has approximately 4,294,967,296 addresses

IP version 6 (IPv6)

• Deployed in 1992
• Uses a 128-bit (16 bytes) addressing scheme
• Address format is Hexadecimal Notation, like 3FFE:F200:0234:AB00:0123:4567:8901:ABCD
• 3FFE:F200:0234::/48 is a Prefix Notation example
• IPv6 has ~340,282,366,920,938,463,374,607,431,768,211,456 addresses

Network Identifiers via TCP/IP

• MAC address is the unique physical address of computers
• MAC addresses are assigned by the manufacturer of the network interface card
• OUI (Organizational Unique Identifier) is the first 24 bits of the MAC address
• The OUI is vendor-specific, identifying the company that made the device
• Vendor-Assigned refers to the remaining 24 bits of the MAC address
• The Vendor-Assigned uniquely identifies the serial number of the individual device and assigned by the specific vendor

IP Addresses

• An IP address uniquely identifies each device on an IP network
• It is commonly assigned by the network administrator or internet service provider
• Public IP address enables computers to find each other online
• Public IP addresses are assigned by the ISP upon connection to the Internet gateway
  • Static public IP addresses are fixed and used for hosting web pages or internet services
  • Dynamic public IP address is chosen from a pool and changes each time one connects to the internet
• Private IP addresses are used by computers on a network to communicate with the router
• Private IP addresses can change each time they connect

Parts of an IP Address

• The network ID/field indicates the host is on the same physical network
• The host ID identifies the individual host within a network

Classes of IPv4 Addresses

• Class A addresses uses the first octet to indicate the network address
• Class A addresses range from 1.0.0.0 to 127.0.0.0
• The format for Class A addresses is Network.Host.Host.Host
• Class A addresses use 24 bits for the host
• Class A networks have a maximum of 16,777,214 hosts
• Class B addresses uses the first two octets to indicate the network address
• Class B addresses range from 128.0.0.0 to 191.255.255.255
• The format for Class B addresses is Network.Network.Host.Host
• Class B addresses use 16 bits for the host
• Class B networks have a maximum of 65,534 hosts
• Class C addresses uses the first three octets to identify the network
• Class C addresses range from 192.0.0.0 to 233.255.255.255
• The format for Class C addresses is Network.Network.Network.Host
• Class C addresses use 8 bits for the host
• Class C networks have a maximum of 254 hosts
• Class D addresses are created to enable multicasting using an IP address
• Class D addresses range from 224.0.0.0 to 239.255.255.255 and are in Host.Host.Host.Host format
• The first four bits of Class D addresses must be 1110
• This makes the first octet range from 224 to 239
• Class E addresses are reserved by the IETF for research
• Class E addresses range from 240.0.0.0 to 255.255.255.255
• The first four bits of Class E is set to "1111"
• The resultant octet range is 240 to 255

IANA IPv4 Special-Purpose Addresses

• Loopback/Localhost Addresses (127.0.0.0 – 127.255.255.255) are used for testing and debugging
• Default Network (0.0.0.0) is used for routing internet datagram (TCP)
• Network Broadcast (255.255.255.255) is used for broadcasting messages
• Private-use addresses are preconfigured for extending IPv4 spaces
  • Private-use addresses include 10.0.0.0 – 10.254.254.254, 172.16.0.0 – 172.16.254.254 and 192.168.0.0 – 192.168.254.254
• Link-Local Addresses (169.254.0.0 – 169.254.254.254) are selected and configured if DHCP is not present

Subnet Mask

• Subnet masks determine the network and host portions of an IP address
• Subnet masks are represented by four octets
• Network bits are represented by 1s, and node bits by 0s

Default Mask

• Class A default mask: 255.0.0.0 (/8)
• Class B default mask: 255.255.0.0 (/16)
• Class C default mask: 255.255.255.0 (/24)
• Class D & E are used for Multicast and Research purposes
• Default Gateway is to specify the address of the nearest routing device

Dotted-Binary to Dotted-Decimal Conversion

• An IP address of 117.149.29.2 is written in dotted-decimal notation

Subnet Masking

• To determine where to break the IP address, the IP address must be "ANDed" with its default mask in binary

Converting IPv4 Addresses

• Convert IPv4 address from decimal into binary
  • Divide the given decimal number by 2 and note down the remainder (Step A)
  • Divide the obtained quotient by 2, and note the remainder again (Step B)
  • Repeat the above steps until you get 0 as the quotient (Step C)
  • Write the remainders in reverse order (Step D)

Determining the network portion

• The Least Significant Bit (LSB) of the binary number is at the top and the Most Significant Bit (MSB) is at the bottom

Subnetting

• Subnetting is borrowing bits from the host ID field to form a new subnet ID field

Steps for Determining the Class and Subnet Mask

• Determine the class and the default mask of the IP address
• Identify the number of subnets required
• Determine how many bits are required to support the total number of subnets
• Determine the custom subnet mask for our network by masking.

Calculating Valid Network IDs

• Determine the valid network IDs by using the smallest bit of the custom subnet mask
• List each subnet address starting with the incremental value
• Total number of subnets = 2s – 2
• Total number of hosts = 26 – 2 = 62

###Determining Host Addresses

• Count the remaining bits (zero's) to the right-hand side of the custom subnet mask
• Total number of hosts = 2h- 2

IPv6 Addresses and Notation

• The scale of Internet expansion was unforeseen
• IETF launched NAT and CIDR to delay IPv4 exhaustion
• IANA announced final IPv4 allocation on February 3, 2011
• The last batch of /22 IPv4 allocation was created November 25, 2019
• IPv6 became a Draft Standard December 1998, ratified July 14, 2017
• IPv6, or IP Next Generation (IPng), is an upgraded version of IPv4
• IPv6 addresses are 128 bits long and divided into eight segments using colons
• Each segment contains 16 bits, and is expressed in hexadecimal notation

IPv6 Address Formats

• An IPv6 address is expressed using IPv6 address/mask length format
  • Example: 2001:0DB8:2345:CD30:1230:4567:89AB:CDEF/64
    • IPv6 address: 2001:0DB8:2345:CD30:1230:4567:89AB:CDEF
    • Subnet number: 2001:0DB8:2345:CD30::/64

IPv6 Abbreviation Specifications

• The leading 0s in each 16-bit segment can be omitted
• If all bits in a 16-bit segment are 0s, at least one 0 must be reserved
• A double colon (::) represents consecutive 16-bit segments containing only 0s
• Only one :: is allowed in an entire IPv6 address
• Abbreviated IPv6 addresses with two double colons (::) cannot be restored to the original.

IPv6 Address Classification

• Unicast address identifies an interface, sending packets to the interface having that address
  • Unspecified address: 0:0:0:0:0:0:0:0/128, or ::/128, used as the source address of some packets
  • Loopback address: 0:0:0:0:0:0:0:1/128, or ::1/128, used for local loopback tests
• Multicast address identifies multiple interfaces, sending packets to all interfaces in the multicast group
  • Only interfaces in a multicast group listen to packets for that group
  • IPv6 does not define any broadcast address, with IPv6 multicast serving all broadcast application scenarios
• Anycast address identifies a group of network interfaces, routing packets to the nearest interface having that address