Bind 9 Administrator Reference Manual

Chapter 6. BIND 9 Configuration Reference
The default is unlimited, meaning that records are purged from the cache only when their TTLs
expire.
6.2.14.9. Periodic Task Intervals
cleaning-interval
The server will remove expired resource records from the cache every cleaning-interval minutes.
The default is 60 minutes. If set to 0, no periodic cleaning will occur.
heartbeat-interval
The server will perform zone maintenance tasks for all zones marked as dialup whenever this
interval expires. The default is 60 minutes. Reasonable values are up to 1 day (1440 minutes). If set
to 0, no zone maintenance for these zones will occur.
interface-interval
The server will scan the network interface list every interface-interval minutes. The default is 60
minutes. If set to 0, interface scanning will only occur when the configuration file is loaded. After
the scan, listeners will be started on any new interfaces (provided they are allowed by the listen-on
configuration). Listeners on interfaces that have gone away will be cleaned up.
statistics-interval
Nameserver statistics will be logged every statistics-interval minutes. The default is 60. If set to 0,
no statistics will be logged.
Note: Not yet implemented in BIND9.
6.2.14.10. Topology
All other things being equal, when the server chooses a nameserver to query from a list of nameservers,
it prefers the one that is topologically closest to itself. The topology statement takes an
address_match_list and interprets it in a special way. Each top-level list element is assigned a distance.
Non-negated elements get a distance based on their position in the list, where the closer the match is to
the start of the list, the shorter the distance is between it and the server. A negated match will be assigned
72