ZyXEL Communications P-660HW-Tx v3 Series User Manual page 280

Chapter 18 Remote Management
The following table describes the labels in this screen.
Table 85 Advanced > Remote Management > ICMP
LABEL
ICMP
Respond to
Ping on
Do not respond
to requests for
unauthorized
services
Apply
Cancel
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DESCRIPTION
Internet Control Message Protocol is a message control and error-
reporting protocol between a host server and a gateway to the Internet.
ICMP uses Internet Protocol (IP) datagrams, but the messages are
processed by the TCP/IP software and directly apparent to the
application user.
The ZyXEL Device will not respond to any incoming Ping requests when
Disable is selected. Select LAN to reply to incoming LAN Ping requests.
Select WAN to reply to incoming WAN Ping requests. Otherwise select
LAN & WAN to reply to both incoming LAN and WAN Ping requests.
Select this option to prevent hackers from finding the ZyXEL Device by
probing for unused ports. If you select this option, the ZyXEL Device will
not respond to port request(s) for unused ports, thus leaving the unused
ports and the ZyXEL Device unseen. If this option is not selected, the
ZyXEL Device will reply with an ICMP port unreachable packet for a port
probe on its unused UDP ports and a TCP reset packet for a port probe
on its unused TCP ports.
Note that the probing packets must first traverse the ZyXEL Device's
firewall rule checks before reaching this anti-probing mechanism.
Therefore if a firewall rule stops a probing packet, the ZyXEL Device
reacts based on the firewall rule to either send a TCP reset packet for a
blocked TCP packet (or an ICMP port-unreachable packet for a blocked
UDP packets) or just drop the packets without sending a response
packet.
Click this to save your changes.
Click this to restore your previously saved settings.
P-660HW-Tx v3 Series User's Guide