Documentation/networking/alias.txt

   1
   2 IP-Aliasing:
   3 ============
   4
   5 IP-aliases are an obsolete way to manage multiple IP-addresses/masks
   6 per interface. Newer tools such as iproute2 support multiple
   7 address/prefixes per interface, but aliases are still supported
   8 for backwards compatibility.
   9
  10 An alias is formed by adding a colon and a string when running ifconfig.
  11 This string is usually numeric, but this is not a must.
  12
  13 o Alias creation.
  14   Alias creation is done by 'magic' interface naming: eg. to create a
  15   200.1.1.1 alias for eth0 ...
  16
  17     # ifconfig eth0:0 200.1.1.1  etc,etc....
  18                    ~~ -> request alias #0 creation (if not yet exists) for eth0
  19
  20     The corresponding route is also set up by this command.
  21     Please note: The route always points to the base interface.
  22
  23
  24 o Alias deletion.
  25   The alias is removed by shutting the alias down:
  26
  27     # ifconfig eth0:0 down
  28                  ~~~~~~~~~~ -> will delete alias
  29
  30
  31 o Alias (re-)configuring
  32
  33   Aliases are not real devices, but programs should be able to configure and
  34   refer to them as usual (ifconfig, route, etc).
  35
  36
  37 o Relationship with main device
  38
  39   If the base device is shut down the added aliases will be deleted
  40   too.