ZyXEL VoIP Router Prestige 2602R-61 91-006-024004 Manual Do Utilizador

Prestige 2602R Series User’s Guide

166 

Chapter 13 Firewall Configuration

Figure 68   Firewall: Anti Probing

The following table describes the labels in this screen.

 For DoS attacks, the Prestige uses thresholds to determine when to drop sessions that do not 
become fully established. These thresholds apply globally to all sessions.

You can use the default threshold values, or you can change them to values more suitable to 
your security requirements.

Table 48   Firewall: Anti Probing 

Respond to PING 

on

The Prestige does 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 Prestige by probing for 

unused ports. If you select this option, the Prestige will not respond to port 

request(s) for unused ports, thus leaving the unused ports and the Prestige 

unseen. By default this option is not selected and the Prestige 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 Prestige 's firewall 

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

mechanism blocks a probing packet, the Prestige 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.

Back

Click Back to return to the previous screen. 

Apply

Click Apply to save your changes back to the Prestige.

Cancel

Click Cancel to begin configuring this screen afresh.