ZyXEL Communications NBG410W3G - Manual (Page 252)

Chapter 14 DNS
NBG410W3G Series User’s Guide
252
The following table describes the labels in this screen.
14.7 DNS Cache
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.
14.8 Configure DNS Cache
To configure your ZyXEL Device’s DNS caching, click ADVANCED > DNS > Cache. The
screen appears as shown.
LABEL DESCRIPTION
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.
Cancel Click Cancel to exit this screen without saving.