IP address

IPv4

• Address is 32 bit
• RIRs are exhausting their pools of assignable IP addresses
• NAT is omnipresent

IPv4 - unicast link local address

• Must not be routed (link only)
• May be self-assigned (e.g. when no DHCP)
• Range
  • 169.254.0.0 - 169.254.255.255 (169.254/16 prefix)
• Should be dropped if anything else is available (unlike IPv6)

IPv4 - unicast local address (private address)

• May be routed internally but not on public internet
• Defined in RFC 1918
• Ranges
  • 10.0.0.0 - 10.255.255.255 (10/8 prefix)
  • 172.16.0.0 - 172.31.255.255 (172.16/12 prefix)
  • 192.168.0.0 - 192.168.255.255 (192.168/16 prefix)

IPv4 - subnetting

• Splitting a single range into logical groups (subnets)
• IP address has NetworkId (Street Name) and HostId (Building Number) part
• /16 address range can have 2^16 hosts
  • 2^0 = 1 subnet of /16 = 65636 hosts
  • 2^1  = 2 subnets of /17 = 32768 hosts
  • 2^2 = 4 subnets of /18 = 16384 hosts
  • 2^3 = 8 subnets of /19 = 8192 hosts
  • 2^4 = 16 subnets of /20 = 4096 hosts
  • 2^5 = 32 subnets of /21 = 2048 hosts
  • 2^6 = 64 subnets of /22 = 1024 hosts
  • 2^7 = 128 subnets of /23 = 512 hosts
  • 2^8 = 256 subnets of /24 = 256 hosts
  • 2^9 = 512 subnets of /25 = 128 hosts
  • 2^10 = 1024 subnets of /26 = 64 hosts
  • 2^11 = 2048 subnets of /27 = 32 hosts
  • 2^12 = 4096 subnets of /28 = 16 hosts (smallest possible VPC subnet)
  • 2^13 = 8192 subnets of /29 = 8 hosts
  • 2^16 = 65536 subnets of /32 = 1 host

IPv5

• Compatible with IPv4
• Had Quality of Service (QoS) built-in
• Never became standard

IPv6

• Successor of IPv4
• Address is 128 bit
• End-to-end connectivity 
  • No need for NAT

IPv6 - unspecified address

• :: (all zeroes)
• Indicates lack of address
• Used in Duplicate Address Detection (DAD)
  • Source: 0:0:0:0:0:0:0:0
  • Target: desired address

IPv6 loopback address

• talk to myself

IPv6 - unicast link local address

• required (unlike IPv4)

IPv6 - unicast local address

• Possible but discouraged
  • Break end-to-end connectivity 

IPv6 - unicast global address

• Recommended way of addressing
• AWS assigns by DHCP

IPv6 - prefixes

• Counterpart of IPv4 subnetting
• Typically
  • First 64 bits are network
  • Last 64 bits are host

IPv6 - notation

• 8 groups of 4 hexadecimal characters
  • 8 groups of "hextet"
• Leading consecutive "0" may be omitted
• 0000:0000:0000 = ::
• Example
  • 2001:0000:0eab:DEAD:0000:00A0:ABCD:004E

References

• https://www.youtube.com/watch?v=GE_FqZ-XLR0
• http://www.potaroo.net/ispcol/2018-01/addr2017.html