ZyXEL Communications G-2000 Plus User Manual

ZyAIR G-2000 Plus User’s Guide

167 

Chapter 12 Remote Management Screens

Figure 72   Security

The following table describes the labels in this screen.

Table 56   Security

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 ZyAIR 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 ZyAIR by probing for unused 

ports. If you select this option, the ZyAIR will not respond to port request(s) for 

unused ports, thus leaving the unused ports and the ZyAIR unseen. By default this 

option is not selected and the ZyAIR 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 ZyAIR's firewall mechanism 

before reaching this anti-probing mechanism. Therefore if the firewall mechanism 

blocks a probing packet, the ZyAIR reacts based on the firewall policy, which by 

default, is to send a TCP reset packet for a blocked TCP packet. You can use the 

command "sys firewall tcprst rst [on|off]" to change this policy. When the firewall 

mechanism blocks a UDP packet, it drops the packet without sending a response 

packet.

Apply

Click Apply to save your customized settings and exit this screen. 

Reset

Click Reset to begin configuring this screen afresh.