ZyXEL Communications 5 Series - Manual (Page 445)

ZyWALL 5/35/70 Series User’s Guide
Chapter 25 DNS 445
25.7 DNS Cache
DNS cache is the temporary storage area where a router stores responses from DNS servers.
When the ZyWALL receives a positive or negative response for a DNS query, it records the
response in the DNS cache. A positive response means that the ZyWALL 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 ZyWALL did not receive a response for a
query it sent to a DNS server within the five second DNS timeout period.
When the ZyWALL receives DNS queries, it compares them against the DNS cache before
querying a DNS server. If the DNS query matches a positive entry, the ZyWALL responses
with the IP address from the entry. If the DNS query matches a negative entry, the ZyWALL
replies that the DNS query failed.
25.8 Configure DNS Cache
To configure your ZyWALL’s DNS caching, click ADVANCED > DNS > Cache. The screen
appears as shown.
Figure 236 ADVANCED > DNS > Cache