Documentation/networking/alias.txt

/* */
NET_ALIAS device aliasing v0.4x
===============================
  The main step taken in versions 0.40+ is the implementation of a
  device aliasing mechanism that creates *actual* devices.
  This development includes NET_ALIAS (generic aliasing) plus IP_ALIAS
  (specific IP) support.

Features
--------
o  ACTUAL alias devices created & inserted in dev chain
o  AF_ independent: net_alias_type objects. Generic aliasing engine.
o  AF_INET optimized
o  hashed alias address lookup
o  net_alias_type objs registration/unreg., module-ables.
o  /proc/net/aliases & /proc/net/alias_types entries

o IP alias implementation: static or runtime module.

Usage (IP aliasing)
-------------------
  A very first step to test if you are running a net_alias-ed kernel
  is to check /proc/net/aliases & /proc/net/alias_types entries:
     # cat /proc/net/alias*

  For IP aliasing you must have IP_ALIAS support included by
  static linking ('y' to 2nd question above), or runtime module
  insertion ('m' to 2nd q. above):
     # insmod /usr/src/linux/modules/ip_alias.o (1.3.xx)
     # insmod /usr/src/ip_alias/ip_alias.o      (1.2.xx) see above.

o Alias creation.
  Alias creation is done by 'magic' iface naming: eg. to create a
  200.1.1.1 alias for eth0 ...
  
    # ifconfig eth0:0 200.1.1.1  etc,etc....
                   ~~ -> request alias #0 creation (if it not exists) for eth0
    and routing stuff also ...
    # route add -host 200.1.1.1 dev eth0:0  (if same IP network as
                                            main device)
   
    # route add -net 200.1.1.0 dev eth0:0   (if completely new network wanted
                                            for eth0:0)

o Alias deletion.
  Also done by magic naming, eg:

    # ifconfig eth0:0-  0  (maybe any address)
                   ~~~ -> will delete alias (note '-' after dev name)
  alias device is closed before deletion, so all network stuff that
  points to it (routes, arp entries, ...) will be released.
                                   
Alias (re-)configuring
  Aliases *are* devices, so you configure and refer to them as usual (ifconfig,
  route, etc).
  
o Procfs entries
  2 entries are added to help fetching alias runtime configuration:
  a) /proc/net/alias_types
     Will show you alias_types registered (ie. address families that
     can be aliased).
     eg. for IP aliasing with 1 alias configured:

     # cat /proc/net/alias_types
     type    name            n_attach
     2       ip              1      
     
  b) /proc/net/aliases
     Will show aliased devices info, eg (same as above):

     # cat /proc/net/aliases
     device           family address                                
     eth0:0           2      200.1.1.1

Relationship with main device
-----------------------------
  - On main device closing, all aliases will be closed and freed.
  - Each new alias created is inserted in dev_chain just before next
    main device (aliases get 'stacked' after main_dev), eg:
      lo->eth0->eth0:0->eth0:2->eth1->0
    If eth0 is unregistered, all it aliases will also be:
      lo->eth1->0     

Contact
-------
Please finger or e-mail me:
   Juan Jose Ciarlante <jjciarla@raiz.uncu.edu.ar>
   
                                
; local variables:
; mode: indented-text
; mode: auto-fill
; end:
/* */
root/Documentation/networking/alias.txt
