  IP Sub-Networking Mini-Howto
  Robert Hart, hartr@interweft.com.au : 翵 dannybox@nownuri.net
  v1.0, 31 March 1997

    IP Ʈũ  ϴ    Ѵ. 
    Ʈũ  Ȳ  ϴ A,B,C Ŭ Ʈũ
  ȣ ϴ ̴.

  1. Copyright

  2. Introduction
    IP Ʈũ ȣ   ,   ڿ ȿ
   ̿ϴ  ߿.   ϳ IP Ʈũ ȣ 
  ٸ Ʈũ   ֵ ϳ IP Ʈũ ȣ   
    ϰ ִ.   ַ Ŭ C IP Ʈũ ȣ 
   ,  Ģ A, B Ŭ ϰ ȴ.

  2.1 ٸ  
  IP ȣ  ڼϰ ⺻  ˷ִ    ִ. 
  ڰ о ϴ 

  . The Linux Network Administrators Guide
     <http://sunsite.unc.edu/LDP/LDP/nag/nag.html>.

  . The Linux System Administration Guide
     <http://linuxwww.db.erau.edu/SAG/>.

  . TCP/IP Network Administration by Craig Hunt, published by O'Reilly
     and Associates <http://www.ora.com/catalog/tcp/noframes.html>.

  3. IP ȣ غ
  Ʈŷ ſ ϱ   IP ȣ  ⺻  
   Ѵ.

  3.1 IP ȣ ȣƮ ƴ ̽  ̴.
  ٵ  ߸  ⺻  и ؾ Ѵ. IP ȣ
  ȣƮ Ҵ  ƴϴ. IP ȣ ȣƮ Ʈũ ̽ 
  Ҵ ̴. (κ ƴ) IP Ʈũ ϴ ǻͰ
  ϳ Ʈũ ̽ (׸   ϳ IP ȣ
  ), ̷ 츸 ִ  ƴϴ. ǻͿ ٸ ̽ 
  ( ʴ) Ʈũ ̽ . ׸   
  Ʈũ ̽  IP ȣ . ׷Ƿ 6 Ȱȭ 
  ̽  ̽ 6 IP ȣ . ׸  IP 
  ȣ   Ʈũ  ̽ Ҵȴ.   
  IP Ʈũ   Ȯ.

  ׷ ұϰ, κ  IP ȣ   밳 ȣƮ ּҸ 
  Ѵ. ⼭ ؾ   ̰ ȣƮ ϴ Ư 
  ̽  IP ȣ ٿ ĪѴٴ ̴. ͳݿ ϴ 
   ̽ (ټ ƴϴ) ϳ ̽ Ƿ ϳ 
  IP ȣ .

  3.2 "Dotted Quads" ǥ IP ȣ 
   IP ȣ  Ϳ (IPv4), IP ȣ 4(8Ʈ) Ʈ 
  Ǿ  32Ʈ Ͽ  ǥѴ.      ǥ
   ִ.(10 ǥ Ǵ). ׸  б  IP ȣ
  밳 "dotted quad"  ǥȴ. IP ȣ
        192.168.1.24
   (.)  4 (10) ̴.

  4   8Ʈ Ʈ 10 ǥ ̰,  4 ڴ 0
  255 ǥ  ִ.(⼭ ؾ   0 ϳ ̹Ƿ 
  256 ̴)

   ȣƮ IP ȣ Ϻδ ȣƮ ġ Ʈũ ǥϰ,  
   ȣƮ(Ʈũ ̽)  ü ǥѴ. Ȯϰ   Ʈ
   Ʈũ ID ǰ, Ʈũ ִ ȣƮ ϴµ   Ʈ
   Ǵ° ϴ  Ʈũ 'Ŭ' ȴ.

  3.3 IP ȣ Ŭ
  IP ȣ 3 Ŭ ִ.( : δ ƼĳƮ    
  Ŭ D Ƿ 4̴. Ŭ D 224.0.0.0-240.0.0.0 ּҸ
  )
  
  . Ŭ A IP ȣ Ʈũ ϴµ   8 Ʈ(dotted quad
     ) ϰ,  24Ʈ(   dotted quad) Ͽ
    Ʈũ ̽ Ѵ.
    Ŭ A ּ   Ʈ ׻ 0̴ -  ù ° dotted quad 
     0 127  . ׷Ƿ ִ 128 Ŭ A 
    Ʈũ ȣ ϰ,  33,554,430   ̽ 
    . ׷ Ʈũ 0.0.0.0(⺻ Ʈ(default route))  127.0.0.0
    (  Ʈũ) Ư ǹ̸    Ʈũ ϴµ
     ʴ´. ׷Ƿ 126 Ŭ A Ʈũ ȣ  
    ִ.

  . Ŭ B IP ȣ Ʈũ ϴµ  16 Ʈ( 2 
    dotted quad) ϰ  16Ʈ( 2 dotted quad) Ͽ
    ȣƮ ̽ Ѵ. Ŭ B ּҴ   Ʈ 2  
    Ʈ ׻ 10 .( : 2 ǥϸ 10xxxxxx.xxxxxxxx
    .xxxxxxxx.xxxxxxxx). ׷Ƿ  14Ʈ Ͽ 32767 Ŭ B 
    Ʈũ   ִ. ׷Ƿ Ŭ B Ʈũ dotted quad 
    ù ° Ʈ  128 191  ,  Ʈũ 
    ִ 32,766 ̿  ̽ .

  . Ŭ C IP ȣ ó 24Ʈ Ͽ Ʈũ ϰ,  
    8Ʈ ȣƮ ̽ Ѵ. Ŭ C ּҴ  3 Ʈ 
    ׻ 110̰ų dotted quad 192 255  . ׷Ƿ 
      Ŭ C Ʈũ ȣ 4,194,303̰  254 
    ̽ . (ù° Ʈ 223 ū Ʈũ ̹ 
    Ǿ ־   )

  ϸ
     
     Ʈũ Ŭ            ù ° Ʈ ()
           A                           1  126
           B                         128  191
           C                         192  254

  'unconnected' Ʈũ  ̸  Ư ּҰ ִ.  IP 
   ϴ Ʈũ ͳݿ Ǿ  ʴ ͵̴.  ּҵ

  . Ѱ Ŭ A Ʈũ
    10.0.0.0
  . 16 Ŭ B Ʈũ
    172.16.0.0 - 172.31.0.0
  . 256 Ŭ C Ʈũ 
    192.168.0.0 - 192.168.255.0

    '' Ʈũ ȣƮ ȥ ϱ  
   ̴.

  3.4 Ʈũ ȣ, ̽ ּҿ εĳƮ ּҵ

  IP ȣ 3 ǹ̸   ִ.

  . IP Ʈũ ּ(  Űü ϴ IP ̽ ׷ 
    -  ̴ ׸Ʈ ϴ  ͵). Ʈũ ȣ ׻ ּ 
     ̽(ȣƮ) Ʈ 0 Ѵ. (Ʈũ  
     ʴ)

  . IP Ʈũ  εĳƮ ּ(ּҴ IP Ʈũ  ̽
    ÿ '̾߱'ϱ  ȴ.). Ʈũ  εĳƮ ּҴ
    ̽(ȣƮ) Ʈ 1 Ѵ.( Ʈũ  
     ʴ )

  . ̽ ּ(ȣƮ ִ ̴ ī峪 PPP ̽, 
    ,   ).  ּҵ  0 ̰ų 1 츦   
       ִ.  ȣƮ Ʈ  0̸  ּҴ Ʈũ 
    ּҰ ǰ, ȣƮ Ʈ  1̸  ּҴ εĳƮ ּҰ ȴ.

  ϸ
  Ŭ A Ʈũ 
  (1Ʈ Ʈũ ּ  3Ʈ ȣƮ ּ )
    10.0.0.0  ּ  ȣƮ Ʈ 0̹Ƿ Ŭ A Ʈũ ȣ̴.
    10.0.1.0   Ʈũ  ȣƮ ̴ּ.
    10.255.255.255  ּ  ȣƮ Ʈ 1̹Ƿ  Ʈũ 
    εĳƮ ̴ּ.

  Ŭ B Ʈũ 
  (2Ʈ Ʈũ ּ  2Ʈ ȣƮ ּ )
    172.17.0.0  Ŭ B Ʈũ ȣ̴.
    172.17.0.1   Ʈũ  ȣƮ ̴ּ.
    172.17.255.255  Ʈũ εĳƮ ̴ּ.

  Ŭ C Ʈũ 
  (3Ʈ Ʈũ ּ  1Ʈ ȣƮ ּ )
    192.168.3.0  Ŭ C Ʈũ ȣ̴.
    192.168.3.42   Ʈũ  ȣƮ ȣ̴.
    192.168.3.255  Ʈũ εĳƮ ̴ּ.

   ȣƮ Ҵ  κ IP Ʈũ ȣ Ŭ C ̴ּ.

  3.5. Ʈũ ũ(network mask)

  Ʈũ ũ ' ũ' ҷ  Ȯϴ. ׷ 밳 
  Ʈũ ũ θ.
   
  ⼭ 츮    ִ  IP ּҰ IP Ʈũ  
    ؼǴ Ʈũ ϸ, ̰ Ʈŷ
  ¸ Ѵ.

  ⺻ Ʈũ ũ  Ʈũ Ʈ '1'̰  ȣƮ Ʈ
  '0'̴. ̰͵  Ŭ Ʈũ  ⺻ Ʈũ 
  ũ̴:-
  
  . Ŭ A Ʈũ ũ: 255.0.0.0

  . Ŭ B Ʈũ ũ: 255.255.0.0

  . Ŭ C Ʈũ ũ: 255.255.255.0

  Ʈũ ũ  ؾ  ΰ ߿  ִ:-

  . Ʈũ ũ   IP ȣ  ؼ  ģ.
    (⼭ ''̶ Ư Ʈũ κ ǹѴ)

  . Ʈũ ũ IP ȣ ƴϴ - ̰  IP ȣ  
     ؼǴ   ȴ.

  4. ̶ ΰ?

  ̶ ϳ IP Ʈũ ּҸ    ϳ Ʈũ IP 
  ּҰ      Ʈũ   ֵ ϴ
  ̴.

  ⼭ ߿ ܾ ''  ̴. ӽ ٱ   
   IP Ʈũ ԵǴ  Ʈũ   ٲ  
  ϳ IP Ʈũ̴. ؾ   ϳ IP Ʈũ  ϳ 
  Ʈũ   ִٴ ̴.

  5.   ϳ?
  
  Ʈŷ ϴ  ˷ â IP Ծ ߴ 
  ư Ѵ. ̶ Ŭ A Ʈũ ȣ 鼭  鸸 ȣƮ 
    ־   Ʈ ߴ.
  
   Ŵ Ʈ ִ  IP ǻ͵   Ʈũ Ǳ
  Ѵٸ û ƮȰ   ߻  ߴ: 
  Ʈũ ϴ  Ŵ  ⸣ Ͱ  Ǹ ̰, 
  Ʈũ Ƹ ( Ȯ) ڽ Ʈ  ر ̾.

   Ʈŷ ϸ: Ŭ A Ʈũ ȣ  Ʈũ
  е ̴.    Ʈũ     ̴.
 
  ̰ ۰ ϱ () Ʈũ   ǹѴ. 
  - и  ٸ Ʈũ  ̿ϸ鼭. ׷   
  Ʈũ ̴, ū , FDDI, ATM    .

  Ʈŷ ϴ ٸ :-
  
  .  Ʈ   Ʈĵ  Ǿ  
    (̺ ̵)   ִ. Ʈŷ ϳ IP ȣ 
    Ͽ IP ȯ泻 ̰͵ ϵ Ѵ.
     ̷ ϵ   鿡  Ʈũ  IP
    ȣ(static IP number) ְ ;ϴ ISP(Internet Service Provider)鿡 
     ſ  ̷ ִ.

  . Ʈũ Ʈ ɰ ӵ ϸ ų   . 
    Ʈũ  ν  Ʈũ   Ʈ 
      ǵ   ִ.   ü Ʈ ٿ 
     Ʈũ 뿪  ʰ Ʈũ ӵ ų  
    ִ.

  . Ȼ 䱸  ٸ Ŭ ִ ڵ  Ʈũ 
      - Ʈũ  ƴ  ׻ ٸ Ʈũ Ʈ ç 
     ִ. Ʈŷ  μ R & D μ Ʈũ Ʈ
    ĺ ϰ Ѵ.(Ȥ л  Ʈũ ĺ ϵ 
    ϰų)!    

  .  ȣȯ ʴ Ʈŷ  ϴ  ̿ϸ鼭, ̵ ̿
    ȣ  ʿѴ.

  6. IP Ʈũ ȣ   

   IP Ʈũ ȣ   ʿ䰡 ִٰ ߴٸ  
   ؾұ? Ʒ  ؾ  ϵ ڼ ϰ ִ.

  .   Ѵ.(Ʈũ  Ϳ  Ʈũ )
  
  . ݿ  ̽ κ  󸶳 Ŀ  Ѵ.
    ٽ ϸ    󸶳  IP ȣ ʿ  Ѵ.

  .  Ʈũ ũ Ʈũ ּҸ Ѵ.

  . Ʈũ  ̽  IP ּҿ  Ʈũ ũ 
    ҴѴ.

  . Ϳ Ʈ ϰ Ʈũ ̽  Ʈ̿ 
    Ʈ ׸/Ȥ ⺻ Ʈ Ѵ. 

  . ý ׽Ʈغ  ߰ߵǸ ģ. ׸ Ѽ . ^^

      ϳ Ŭ C Ʈũ ȣ 192.168.1.0 
     Ѵ.

   IP Ʈũ ִ 254 ̽(ȣƮ)   ְ, ݵ 
  Ʈũ ڽ ǥ Ʈũ ȣ(192.168.1.0) ׸ εĳƮ ּ
  (192.168.1.255) .

  6.1   ϱ

    ؾ Ʈũ    յǵ  
  ̽ ȣ ǵ ϱ Ȯ ̺ Ʈ
  (infrastructure) ġؾ  ̴.

    پ κ(, ̵ ȯ ) ȣ Ҽ ִ 
  Ŀ ʿ  𸥴.

  и ̰Ϳ  ڼ  Ұϴ.  ʿϴٸ ̷ 񽺸
  ϴ  Ʈũ /ġ    .  
   ׷   Ǵ     ִ. 
  (comp.os.linux.networking   ׷)

  6.2.   ũ ϱ

      'Ҿ' IP ȣ  ̿
  Ÿ ʿϴ.

    IP Ʈũ 2 ּҸ ̽(ȣƮ) ּҷ 
    ȴ - Ʈũ IP ȣ  ü εĳƮ ּ. 
   ϸ   Ʈũ ڽ ǥ  IP Ʈũ 
  ȣ εĳƮ ȣ ʿ ϸ,  ȣ  IP Ʈũ
      ȿ ̾ Ѵ.

  ׷Ƿ IP Ʈũ ΰ  иϴ  2 Ʈũ
  ּҿ ΰ εĳƮ ʿϴٴ ̹Ƿ, ̴  'Ұ'
  ̽ (ȣƮ) ּҰ Ѵٴ  ǹѴ.  4 
  Ʈũ ٸ  ڴ 8 ϰ ȴ.

     ݵ 4 IP ȣ Ǿ ִ.

  . ΰ 밡 IP ̽ ȣ- Ѱ  Ʈũ  
    ̽  ̰  Ѱ  Ʈũ ̱ ȣƮ  

  . Ѱ Ʈũ ȣ

  . Ѱ εĳƮ ּ

   ̷  ϴ IP ڸ ÿ鼭  Ʈũ   ϴ
    ٸ ̴. Ʈũ  ϳ ȣƮ ִٸ  
  Ʈũ ŵ ٸ Ʈũ  Ѵ. ׷  Ե  
  ݿ Ǵ  ü Ģ   ̴.

  ̷ IP Ʈũ ȣ Ȱ ũ⸦(   
  Ʈũ   ִ.)  2^n    
  ִ.(̶ n  IP Ʈũ ȣ ȣƮ Ʈ  
  ϳ  ̴)

  ׷Ƿ ڽ Ʈũ ϴµ ̾ Ѵ -  , 
   , Ȼ ѵ Ͽ ϸ  Ʈũ 
  ڸ ̴   ؾѴ. 

  6.3.   ũ Ʈũ ȣ ϱ

  IP Ʈũ    ϴ  Ʈũ ũ
  ̴.

     IP Ʈũ ȣ  Ʈũ ũ
  ܼ Ʈũ ȣ  'Ʈũ Ʈ' '1' ϰ  
  ȣƮ Ʈ '0'  ̴. 

  ׷Ƿ IP ȣ  Ŭ  ǥ Ʈũ ũ  
  .

  . Ŭ A (8 Ʈũ Ʈ) : 255.0.0.0

  . Ŭ B (16 Ʈũ Ʈ): 255.255.0.0

  . Ŭ C (24 Ʈũ Ʈ): 255.255.255.0

   ϴ  ϳ Ȥ  ̻ 밡 ȣƮ Ʈ
  ͼ ̽  Ʈ Ʈũ Ϻη ؼϵ ϴ ̴.
  ׷Ƿ Ʈũ ȣ ΰ   ؼ ù°
  ȣƮ Ʈũ ũ Ʈ  Ʈ '1' Ͽ Ѱ ȣƮ
  Ʈ ´.

  Ŭ C ּҿ  Ʈũ ũ 11111111.11111111.11111111.10000000
  Ǵ 255.255.255.128 ȴ.

  츮 캸 ִ Ŭ C Ʈũ ȣ 192.168.1.0  е
    ɼ   ִ. 
  ______________________________________________________________________
  No of      No of
  subnets    Hosts/net    netmask
  2            126        255.255.255.128 (11111111.11111111.11111111.10000000)
  4             62        255.255.255.192 (11111111.11111111.11111111.11000000)
  8             30        255.255.255.224 (11111111.11111111.11111111.11100000)
  16            14        255.255.255.240 (11111111.11111111.11111111.11110000)
  32             6        255.255.255.248 (11111111.11111111.11111111.11111000)
  64             2        255.255.255.252 (11111111.11111111.11111111.11111100)
  ______________________________________________________________________

  ̷, ó  鶧 ݵ Ʈũ ũ Ʈ 
   ߿ ȣƮ Ʈ   ߿ ȣƮ Ʈ  ʿ
  .  ׷      ʴ´ٸ  IP
  ȣ ſ ̻   ̴.   2 ͼġ ʴ 츮
  ν IP ȣ  ݿ ִ ˱Ⱑ ſ .
  (ݸ ǻʹ    ߴ    ̴)

   Ʈũ ߴٸ   Ʈũ ּҿ εĳƮ
  ּҿ  Ʈũ IP ȣ  ˾ƾ Ѵ. ٽ ѹ 
    Ŭ C IP Ʈũ ȣ ϰ  ȣƮ ȣ
  ֵ ϰڴ.  

  --------------------------------------------------------------------------
  Netmask         Subnets Network B'cast  MinIP   MaxIP   Hosts  Total Hosts
  --------------------------------------------------------------------------
      128            2       0     127       1     126    126
                           128     255     129     254    126     252

      192            4       0      63       1      62     62
                            64     127      65     126     62
                           128     191     129     190     62
                           192     255     193     254     62     248

      224            8       0      31       1      30     30
                            32      63      33      62     30
                            64      95      65      94     30
                            96     127      97     126     30
                           128     159     129     158     30
                           160     191     161     190     30
                           192     223     193     222     30
                           224     255     225     254     30     240
  ______________________________________________________________________

   ̴ ó ̵ ڿ   ϱ  ȮϱⰡ 
  ſ . Ʈŷ Ʒ  ڰ Կ  밡 
  ȣƮ ּ ü ڰ Ѵٴ  ش.

   κ  е ȣƮ Ʈũ IP ȣ ׸ Ʈũũ
   Ҵ  ְ Ǿ.

  7.  

    ΰ Ʈũ ̽   PC ΰ(Ȥ  ̻)
    Ʈϱ  Ѵٸ Ŀο IP (IP Forwarding) 
  ϵ ؾѴ.

  ______________________________________________________________________
          cat /proc/ksyms | grep ip_forward
  ______________________________________________________________________

  ̷    ̴.

  ______________________________________________________________________
  00141364 ip_forward_Rf71ac834
  ______________________________________________________________________

   ̷ ޽ Ÿ ʴ´ٸ  Ŀ IP  ǵ 
    ̹Ƿ Ŀ    ο Ŀ ġؾ Ѵ.

     Ŭ C IP Ʈũ ȣ 192.168.1.0 4 
    Ѵ.( 62 밡 ̽/ȣƮ
  IP ȣ  ȴ). ׷ ̵  ΰ   ū ϳ Ʈũ
   ϵ յ ̹Ƿ    Ʈũ ϰ
  ȴ.
  

  ______________________________________________________________________
  Ʈũ        εĳƮ    Ʈũ              ȣƮ 
  192.168.1.0     192.168.1.63    255.255.255.192         62
  192.168.1.64    192.168.1.127   255.255.255.192         62
  192.168.1.128   192.168.1.255   255.255.255.128         124 (see note)
  ______________________________________________________________________

  :  Ʈũ 124 밡 Ʈũ ּҸ 
  (Ʈũ ũκ   ִ 126 ƴ) ̰ ΰ
  ݿ  ' '̱ ̴. ٸ ΰ Ʈũ ִ ȣƮ
  192.168.1.192 ' ʴ'  Ʈũ ּҷ ؼ ̴. ̿ 
  ϰ 192.168.1.191  ' ʴ'  εĳƮ ּҷ 
  ؼ ̴. 

  ׷Ƿ   192.168.1.191 192 Ʈũ ȣƮ ּҷ
  Ѵٸ    ΰ Ʈũ ϴ ӽŵ ̵   
   ̴.

  ̰  ߿ Ѱ   ش.  밡 ּҴ  
  ּ    ݿ  ȴٴ ̴.

  7.1.   ̺

    ϴ ǻͰ  Ʈũ ͷ Ѵٰ 
  غ.  ǻʹ    3 Ʈũ ̽ 
  ְ Ƹ ׹° ̽  ͳݿ Ǿ  ̴.
  ( ̽ '⺻ Ʈ' ̴.)

    ǻͰ  ݿ   IP ּҸ ̽
  Ѵٰ Ѵ.  Ʈũ ̽   Ǿ
  ̴.

  ______________________________________________________________________
  ̽      IP ּ         ݸũ
  eth0            192.168.1.1     255.255.255.192
  eth1            192.168.1.65    255.255.255.192
  eth2            192.168.1.129   255.255.255.128
  ______________________________________________________________________

  ̰Ϳ     ̴.

  ______________________________________________________________________
   ּ     Ʈ      Genmask         ̽
  192.168.1.0     0.0.0.0         255.255.255.192 eth0
  192.168.1.64    0.0.0.0         255.255.255.192 eth1
  192.168.1.128   0.0.0.0         255.255.255.128 eth2
  ______________________________________________________________________

   ݿ  ȣƮ ڽ IP ȣ Ʈũ ũ 
  Ǿ  ̴.(Ư Ʈũ ϵ)  ȣƮ Ʈũ
   ̽  PC IP ּҸ ν,  ǻ͸ ڽ
  Ʈ/ͷ Ѵ.

  Robert Hart Melbourne, Australia March 1997.


