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Understanding IPv6 Addressing and Conversion

Aug 8, 2024

Lecture on IPv6 Addressing

IPv4 vs IPv6

  • IPv4 uses 32-bit addresses.
    • Limited number of addresses due to high demand.
  • IPv6 uses 128-bit addresses.
    • Translates to a much larger address space.
    • Sufficient for foreseeable future.

Structure of IPv6 Address

  • Written in binary: 128 binary values.
  • Usually shown in hexadecimal format.
  • Divided into 8 groups, each of 16 bits (2 bytes/2 octets):
    • Example: fe80:0000:0000:0000:0000:0000:0000:8f52
    • Abbreviated: fe80::5d18:652:cffd:8f52

Abbreviating IPv6 Addresses

  • Leading Zeros: Can be removed from each group.
  • Groups of Zeros: Can replace multiple groups of zeros with a double colon ::.
    • Only one double colon allowed per address.
  • Example Compression:
    • Original: 2600:dddd:1111:0000:0000:0000:0001
    • Remove Leading Zeros: 2600:dddd:1111:0:0:0:1
    • Compress Zeros: 2600:dddd:1111::1

EUI-64 Format for IPv6 Addresses

  • Statically Assigning IPv6 Address without DHCP:
    • Uses MAC address to create an EUI-64 (64-bit extended unique identifier).
    • MAC address: 48 bits, requires expansion to 64 bits.
  • Process:
    1. Split MAC address into two halves.
    2. Insert ff:fe between the halves.
    3. Change 7th bit to signify locally administered address.
  • Example:
    • Original MAC: 8c:dd:ee:4b:98:a7
    • Split: 8c:dd:ee and 4b:98:a7
    • Insert ff:fe: 8c:dd:ee:ff:fe:4b:98:a7
    • Change 7th bit: 8e:dd:ee:ff:fe:4b:98:a7

Changing the 7th Bit

  • Purpose: Convert from universal to locally administered address.
  • Bit Manipulation:
    • 7th bit of first byte: Changes from 8c to 8e (binary: 10001100 to 10001110)
  • Shortcut Chart:
    • Create a conversion chart for quick reference.
    • Example: 8 -> a, c -> e.

Practical Examples

  • Example MAC Address Conversions
    • MAC: 8c:2d:aa:4b:98:a7
      • Converted EUI-64: 8e2d:aa:fffe:4b98:a7
    • MAC: 18:xx:xx:xx:xx:xx
      • Converted EUI-64: 1aff:fe:xx:xx:xx:xx
    • MAC: a0:xx:xx:xx:xx:xx
      • Converted EUI-64: a2ff:fe:xx:xx:xx:xx
    • MAC: 34:xx:xx:xx:xx:xx
      • Converted EUI-64: 36ff:fe:xx:xx:xx:xx

These notes cover the key concepts and processes for understanding and working with IPv6 addresses, including address structure, abbreviation techniques, and the creation of EUI-64 addresses from MAC addresses.

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