A great number of IP that entered to server, could that client that want to enter. just direct block ip and mac address him from firewall configuration

1. Login to mikrotik used Winbox

2. then from winbox block ip

/ip firewall filter add chain=forward src-address=123.123.123.10 action=drop

3. Block ip and Mac address

from winbox

ip firewall filter add chain=forward src-address=123.123.123.10 src-mac-address= oe:09:j8:kl:9a

And don’t forget to be given the sign (! ) nearby left this MAC OK

4. To Tab Action chose Action: drop

5. click “apply” and “ok”

Source : http://mikrotik.unimedcenter.org/?p=18