Device Type DGS-3200-16 Gigabit Ethernet Switch
Firmware Version 1.50.B019
Hardware Version A1
Boot PROM Version 1.00.B012
суть проблемы здесь(в конце переписки):
viewtopic.php?t=123935

Как настроить или защититься от этого:
Description: The number of concurrent TCP connections from the source IP address 193.168.1.57 exceeded the configured limit. As a result, ISA Server will not allow the creation of new TCP connections from this source IP.
This IP address probably belongs to an attacker or an infected host.
See product documentation for more info about ISA flood resiliency.