ZyXEL g-2000 plusv2 Guida Utente

ZyXEL G-2000 Plus v2 User’s Guide

Chapter 13 Remote Management Screens

177

Figure 74   Security

The following table describes the labels in this screen.

Table 61   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 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. 

Do not respond to 

requests for 

unauthorized 

services

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. By default this option is not selected and 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 

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

mechanism blocks a probing packet, the ZyXEL device 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.