ZyXEL P-793H v2 User Guide - Page 249

The ICMP Screen

Page 249 highlights

Chapter 17 Remote Management 17.7 The ICMP Screen To change your P-793H v2'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 P-793H v2, an ICMP response packet is automatically returned. This allows the outside user to know the P-793H v2 exists. Your P-793H v2 supports anti-probing, which prevents the ICMP response packet from being sent. This keeps outsiders from discovering your P-793H v2 when unsupported ports are probed. Note: If you want your device to respond to pings and requests for unauthorized services, you may also need to configure the firewall anti probing settings to match. Figure 114 Advanced > Remote Management > ICMP The following table describes the labels in this screen. Table 76 Advanced > Remote Management > ICMP LABEL DESCRIPTION ICMP Internet Control Message Protocol is a message control and errorreporting 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. Respond to Ping on The P-793H v2 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. Do not respond to requests for unauthorized services Select this option to prevent hackers from finding the P-793H v2 by probing for unused ports. If you select this option, the P-793H v2 will not respond to port request(s) for unused ports, thus leaving the unused ports and the P-793H v2 unseen. If this option is not selected, the P793H v2 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 P-793H v2's firewall rule checks before reaching this anti-probing mechanism. Therefore if a firewall rule stops a probing packet, the P-793H v2 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. P-793H v2 User's Guide 249

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Chapter 17 Remote Management
P-793H v2 User’s Guide
249
17.7
The ICMP Screen
To change your P-793H v2’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 P-793H v2, an
ICMP response packet is automatically returned. This allows the outside user to
know the P-793H v2 exists. Your P-793H v2 supports anti-probing, which prevents
the ICMP response packet from being sent. This keeps outsiders from discovering
your P-793H v2 when unsupported ports are probed.
Note: If you want your device to respond to pings and requests for unauthorized
services, you may also need to configure the firewall anti probing settings to
match.
Figure 114
Advanced > Remote Management > ICMP
The following table describes the labels in this screen.
Table 76
Advanced > Remote Management > ICMP
LABEL
DESCRIPTION
ICMP
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.
Respond to
Ping on
The P-793H v2 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.
Do not respond
to requests for
unauthorized
services
Select this option to prevent hackers from finding the P-793H v2 by
probing for unused ports. If you select this option, the P-793H v2 will
not respond to port request(s) for unused ports, thus leaving the unused
ports and the P-793H v2 unseen. If this option is not selected, the P-
793H v2 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 P-793H v2's
firewall rule checks before reaching this anti-probing mechanism.
Therefore if a firewall rule stops a probing packet, the P-793H v2 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.