[NTLUG:Discuss] network masks

[Cameron]

Okay, after banging my head against the wall, I still don't have a firm
grasp on network masks like the following:

  type              address/mask    netmask
  ----              ------------    -------
  Class B Private   172.16.0.0/12   255.15.0.0
  Class E Reserved  240.0.0.0/5     31.0.0.0
  IANA Reserved     96.0.0.0/4      15.0.0.0
  IANA Reserved     220.0.0.0/6     63.0.0.0

Could someone provide me with some examples of how a half-backed netmask
octet is handled (like 15.0.0.0 as opposed to the standard 255.0.0.0)?

While we are on the subject, is there a good resource online that covers
how netmasking (or networking in general i suppose) works?  I read the
relevant sections of the LDP NAG, but it didn't go very deep into
netmasks nor routing depending on netmasks.  TIA
--
cameron
  [ How do you tell when you're out of invisible ink? ]