Subnetting 192.168.10.0/24

[Ashley M. Kirchner]

    I want to give each department in our building their own subnet and 
I'm a bit confused on how to get that done.

    Right now I have everything under the full range:

----------
    authoritative;
    subnet 192.168.10.0 netmask 255.255.255.0
       range 192.168.10.5 192.168.10.250;  # .1 - .4, .251 - .255 reserved
       max-lease-time 86400;
       default-lease-time 57600;
       min-lease-time 300;
       option routers 192.168.10.1;
       option broadcast-address 192.168.10.255;
       option domain-name-servers 192.168.10.1;
       option ip-forwarding off;
       ddns-update-style interim;
       ignore client-updates;

       # Static Rats
       group {
          host server_1 { hardware ethernet 11:11:11:11:11:11; 
fixed-address 192.168.10.11; }
          host server_2 { hardware ethernet 22:22:22:22:22:22; 
fixed-address 192.168.10.12; }
          host server_3 { hardware ethernet 33:33:33:33:33:33; 
fixed-address 192.168.10.13; }
       }

       # Shippping Kernels
       group {
          host fedex { hardware ethernet 44:44:44:44:44:44; }
          host ups   { hardware ethernet 55:55:55:55:55:55; }
          host rep_1 { hardware ethernet 66:66:66:66:66:66; }
          host rep_2 { hardware ethernet 77:77:77:77:77:77; }
       }

       # Sales Bullies
       group {
          host sales_1 { hardware ethernet 88:88:88:88:88:88; }
          host sales_2 { hardware ethernet 99:99:99:99:99:99; }
       }
    }
----------

    What I'd like to do is give each group their own range, for example:
       # Shipping Kernels gets 192.168.10.32/255.255.255.240 (.32 - .47)
       # Sales Bullies gets 192.168.10.48/255.255.255.240 (.48 - .63)
       etc., etc.

    However, they would all still need to route through the same router 
192.168.10.1.

    Do I simply specify a range within each group and hope for the 
best?  Or do I nix the global subnet{} statement and set each group{} 
with its own subnet?  How does routing work then since each group{} 
would have it's own broadcast ip?