IP Address

The IP address, something like 192.168.0.10, is used to address an IP endpoint. The IP address is typically used to address a single network interface card (NIC). Every NIC used to communicate through IP, must have at least one IP address.

One machine can have a lot of IP addresses, as a machine can have more than one NIC, and a NIC can have more than one IP address (however, that's not widely used).

The IP address can be statically assigned to a NIC through system specific configuration, or dynamically assigned using DHCP or APIPA.

IP address classes

  • 0.1.0.0 - 126.0.0.0 Class A
  • 128.0.0.0 - 191.255.0.0 Class B
  • 192.0.1.0 - 223.255.255.0 Class C
  • 224.0.0.0 - 239.255.255.255 Class D
  • 240.0.0.0 - 247.255.255.255 Class E

Special IP addresses

  • 127.0.0.0 - 127.255.255.255 local loopback, should never appear on the network

  • 169.254.0.0 - 169.254.255.254 link local for use with Automatic Private IP Addressing (APIPA)

  • 224.0.0.0 - 239.255.255.255 multicasting RFC1112, transmission to a host group

  • 255.255.255.255 limited broadcast, send to all nodes

Private IP Addresses

The following IP addresses should be used for private networks:

  • 10.0.0.0 - 10.255.255.255 private in Class A
  • 172.16.0.0 - 172.31.255.255 private in Class B
  • 192.168.0.0 - 192.168.255.255 private in Class C

Stupid Tricks Involving IP Addresses

Most operating systems let you specify an IP address as an integer as opposed to the traditional dotted-quad format. For instance, the following commands are equivalent:

 ping 192.168.5.1
 ping 0xc0a80501   # Hexadecimal
 ping 3232236801   # Decimal
 ping 030052002401 # Octal

External Links

Discussion

What about IPv6? See, for example, RFC 2373. - Guy Harris


Imported from https://wiki.wireshark.org/IP-address on 2020-08-11 23:15:11 UTC