ZyXEL Communications NBG410W3G Series User Manual

Chapter 14 DNS

NBG410W3G Series User’s Guide

The following table describes the labels in this screen.

DNS cache is the temporary storage area where a router stores responses from DNS servers. 
When the ZyXEL Device receives a positive or negative response for a DNS query, it records 
the response in the DNS cache. A positive response means that the ZyXEL Device received 
the IP address for a domain name that it checked with a DNS server within the five second 
DNS timeout period. A negative response means that the ZyXEL Device did not receive a 
response for a query it sent to a DNS server within the five second DNS timeout period. 
When the ZyXEL Device receives DNS queries, it compares them against the DNS cache 
before querying a DNS server. If the DNS query matches a positive entry, the ZyXEL Device 
responses with the IP address from the entry. If the DNS query matches a negative entry, the 
ZyXEL Device replies that the DNS query failed.

To configure your ZyXEL Device’s DNS caching, click ADVANCED > DNS > Cache. The 
screen appears as shown.

Domain Zone

This field is optional.
A domain zone is a fully qualified domain name without the host. For example, 

zyxel.com.tw is the domain zone for the www.zyxel.com.tw fully qualified domain 

name. For example, whenever the ZyXEL Device receives needs to resolve a 

zyxel.com.tw domain name, it can send a query to the recorded name server IP 

address.
Leave this field blank if all domain zones are served by the specified DNS server(s).

DNS Server

Select the DNS Server(s) from ISP radio button if your ISP dynamically assigns 

DNS server information. You also need to select an interface through which the ISP 

provides the DNS server IP address(es). The interface should be activated and set 

as a DHCP client.The fields below display the (read-only) DNS server IP 

address(es) that the ISP assigns. N/A displays for any DNS server IP address fields 

for which the ISP does not assign an IP address. N/A displays for all of the DNS 

server IP address fields if the ZyXEL Device has a fixed WAN IP address. 
Select Public DNS Server if you have the IP address of a DNS server. The IP 

address must be public or a private address on your local LAN. Enter the DNS 

server's IP address in the field to the right. 
Public DNS Server entries with the IP address set to 0.0.0.0 are not allowed. 
Select Private DNS Server if the DNS server has a private IP address and is located 

in a local network. Enter the DNS server's IP address in the field to the right. 
With a private DNS server, you must also configure the first DNS server entry for the 

LAN or DMZ in the DNS DHCP screen to use DNS Relay.
Private DNS Server entries with the IP address set to 0.0.0.0 are not allowed.

Apply

Click Apply to save your changes.

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