Configuring Icmp - ZyXEL Communications P-660R-F1 series User Manual

13.8 Configuring ICMP

To change your ZyXEL Device's security settings, click Advanced > Remote MGMT > ICMP. The
screen appears as shown.
If an outside user attempts to probe an unsupported port on your ZyXEL Device, an ICMP response
packet is automatically returned. This allows the outside user to know the ZyXEL Device exists.
Your ZyXEL Device supports anti-probing, which prevents the ICMP response packet from being
sent. This keeps outsiders from discovering your ZyXEL Device when unsupported ports are probed.
Figure 105 Remote Management: ICMP
The following table describes the labels in this screen.
Table 67 Remote Management: ICMP
LABEL
ICMP
Respond to Ping
on
Do not respond to
requests for
unauthorized
services
Apply
Cancel
P-660R-F1 Series User's Guide
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 Apply to save your customized settings and exit this screen.
Click Cancel to begin configuring this screen afresh.
Chapter 13 Remote Management Configuration
173