ZyXEL Communications NBG6503 User Manual

 Chapter 17 Firewall

NBG6503 User’s Guide

If an outside user attempts to probe an unsupported port on your Router, an ICMP response packet 
is automatically returned. This allows the outside user to know the Router exists. Use this screen to 
prevent the ICMP response packet from being sent. This keeps outsiders from discovering your 
Router when unsupported ports are probed.

You can also use this screen to enable service blocking, enter/delete/modify the services you want 
to block and the date/time you want to block them.

Click Security > Firewall > Services. The screen appears as shown next. 

Figure 92   Security > Firewall > Services 

The following table describes the labels in this screen.

Table 56   Security > Firewall > Services

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 Router 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 all incoming LAN and WAN Ping 
requests. 

Apply

Click Apply to save the settings.