User manual

Appendix D: Domain Name System
188 Cobalt RaQ 4 User Manual
Name server (NS)
The primary name server defaults to the host name of the RaQ 4. You can specify
the qualified host name of the secondary DNS server for that domain in the
Secondary Name Server (NS) host name field. Some top-level domain
registration organizations require that the secondary name server record be
defined.
Domain administrator email address
The email address defaults to the user name admin of the RaQ 4. This email
address is publicly available and is the administrative contact for the domain or
network served.
Refresh interval
You can configure the refresh interval between updates from a secondary DNS
server.
• If DNS record changes occur infrequently, increase the default value.
• If DNS record changes occur often, decrease the default value.
Tune the refresh interval to avoid wasting bandwidth and to ensure the content on
the secondary server is accurate at all times.
Retry interval
Due to a connection or service failure, a secondary DNS server may be unable to
refresh data from the primary server. The secondary DNS server attempts to
refresh data after the interval specified for trying again.
Expire interval
A secondary DNS server may be unable to refresh data from the primary server
for a prolonged period of time. After the interval specified for expiry, the
secondary server stops serving name requests.
Time-to-live period (TTL)
A caching DNS server other than the primary and secondary DNS servers for this
domain or network can cache record lookups for the TTL period. During the TTL
period, a caching DNS server does not poll the primary or secondary DNS
servers for repeated lookups of the same record.