Before that here is the topology of our overall Network
Please have a look at the following image which will represent The network set-up i am talking,
And here is the Information about our LAN
clients-90% of them running windows xp-sp2 and rest running windows 7 and vista.
Servers-each sub-net has a DC i.e server,they are running windows 2003 OS.
Main-server-i.e the 1 that is providing internet access to rest of the clients and other servers in sub-net 1,2,3,4 running red-hat linux.
And switches used in our networks are un-managed one and our network does not have any kind of NIDS,HIDS,NIPS,HIPS or any kind of Network security set-up,..
Traffic or accessing pc's across sub-nets is allowed by the Domain controller,
And LAN or Ethernet speed in a single sub-net is 100 mbps
generating ARP broad-cast across sub-net's ,Also i am not sure about the switch type,because it is kind of OLD and it is a un-managed one with no-IP Address for it..
So looking for some ideas and help,hope i will find some help...