[lug] I'm looking for a kind person

[behapy]

Hi, all

There is strange network construction in my work.  This works fine, but
I can not understand.

router+---21.101.2.1----------------21.101.2.122(IP),
255.255.255.0(SUBNETMASK), 21.101.2.1(GW)
      |                             21.101.4.234    ,
255,255,255,0              21.101.4.1
      |                             21.101.3.221    ,
255,255,255,0              21.101.3.1
      |                             21.101.2.229    ,
255,255,255,0              21,101.4.1(?)
      |                                                  . 
      |                                                  .
      |                                                  . 
      |                                                  .
      |
      +---21.101.3.1----------------21.101.3.112    ,
255,255,255,0              21,101.3.1
      |                             21.101.3.224    ,
255,255,255,0              21.101.3.1
      |                             21.101.3.124    ,
255,255,255,0              21.101.3.1
      |                             21.101.4.24     ,
255,255,255,0              21.101.4.1(?)
      |                                                  . 
      |                                                  .
      |                                                  . 
      |                                                  .
      |
      +---21.101.4.1----------------21.101.4.24     ,
255,255,255,0              21.101.4.1
                                    21.101.4.24     ,
255,255,255,0              21.101.4.1
                                    21.101.4.24     ,
255,255,255,0              21.101.4.1
                                    21.101.4.24     ,
255,255,255,0              21.101.4.1
                                                         .
                                                         .
                                                         .
                                                         .

As you see, I do not think the network construction is correct.  I
didn't confirm that the (?) works fine.  It might be not perfect but
still works.  The all of above works fine in my work.

I think 21.101.2.1 has to be connected to 21.101.2.* and 21.101.3.1 has
to be connected to 21.101.3.*.  I think this is right.  The above is
wrong.

Sometimes I see uncommon subnetmask like 255.255.255.128 at a pc game
room.  I want to know what subnetmask is for.  So,

I'm looking for a person who'll send me a book.  Of course I'll pay the
all of cost.  The book may concern tcp/ip, subnetmask, router, hub
etc..  And it must be easy to understand in general, because I'm not a
native speaker.  I don't think the book is very easy to understand,
because it is a technology book.  I don't care but I wish the book is
easy.

Now, I'm waiting for your help.  Have a nice day.

Best Regards,
Jingun