hi .. there is an annoying problem .. when a single client has a virus or some kind of a network problem ethernet or whatever it affects the whole network of 300+ users !!!
high latencies are observed , wireless links are badly affected ( timeouts and high delays ) .. Another thing if a loop happens how to prevent it from affecting network ..???? please i need answers

Drop SMB and RPC ports. More drastic would be to disable forwarding in the AP, but that would make it so 2 business locations couldnt tunnel a vpn to each other. More information on the infrastructure would be helpful.

There are too few information about your network.
I guess you are using a completely flat L2 network?
That would be a no-go for 300 users!

Do your users connect via CPEs or directly via their computers?
In first case just use pppoe and most of your problems will be gone...

thnx for ur interest .. but no i can't use pppoe . my ISP provided me with ips each for an end-user and all of my clients are on the same network . I use the mikrotik just to let ips passthrough it inorder to make static the mac-addreses and observe the queues not more .. But when any small problem accurs the whole network is affected !! what can i do ?

Are you saying you are running a /23 broadcast network in wireless?

Wow.

plzz can anyone here answer me how to prevent clients on same network to affect each others :s

does /23 network affect broadcast.

i do not hav much idea of subneting but my isp has given me a server with 2 ethernet cards. LAN 1 with public ip and LAN 2 with lan ip 10.10.1.1. My Mikrotik is connected to LaN 2. Customers connect thru CPE CLIENTS to my mikrotik and their PC have IP 10.10.1.2 & 10.10.1.3 and so on. Some user give subnet as 255.0.0.0 and some give 255.255.255.0. The gateway is 10.10.1.1 and DNS is 10.10.1.1. Both type users still connect and access internet. I am facing similar latency issues. I have tried several firewall rules dropping several IP's. Sometimes nothing seems to help. I am apprehending broadcast and virus issue but i do not know how to prevent.

ideas?, I have the same problem on my network.
Thanks