Ping Test; Safeguard Engine - D-Link DES-1228/ME User Manual

DES-1228/ME Layer 2 Fast Ethernet Managed Switch

Ping Test

Ping is a small program that sends ICMP Echo packets to the IP address you specify. The destination node then responds to or
"echoes" the packets sent from the Switch. This is very useful to verify connectivity between the Switch and other nodes on the
network. To view this window click, Administration > Ping Test.
Figure 6- 24. Ping Test window
The user may use Infinite times radio button, in the Repeat Pinging for field, which will tell the ping program to keep sending
ICMP Echo packets to the specified IP address until the program is stopped. The user may opt to choose a specific number of
times to ping the Target IP Address by clicking its radio button and entering a number between 1 and 255. Click Start to initiate
the Ping program.

Safeguard Engine

Periodically, malicious hosts on the network will attack the Switch by utilizing packet flooding (ARP Storm) or other methods. To
alleviate this problem, the Safeguard Engine function was added to the Switch's software.
The Safeguard Engine can help the overall operability of the Switch by minimizing the workload of the Switch while the attack is
ongoing, thus making it capable to forward essential packets over its network in a limited bandwidth. When the Switch either (a)
receives too many packets to process or (b) exerts too much memory, it will enter an Exhausted mode. When in this mode, the
Switch will drop all ARP and IP broadcast packets for a calculated time interval. Every five seconds, the Switch will check to see
if there are too many packets flooding the Switch. If the threshold has been crossed, the Switch will initially stop all ingress ARP
and IP broadcast packets for five seconds. After another five-second checking interval arrives, the Switch will again check the
ingress flow of packets. If the flooding has stopped, the Switch will again begin accepting all packets. Yet, if the checking shows
that there continues to be too many packets flooding the Switch, it will stop accepting all ARP and IP broadcast packets for double
the time of the previous stop period. This doubling of time for stopping ingress ARP and IP broadcast packets will continue until
the maximum time has been reached, which is 320 seconds and every stop from this point until a return to normal ingress flow
would be 320 seconds. For a better understanding, examine the following example of the Safeguard Engine.
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