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22 Chapter 2 DNS Service
To enable or disable recursion:
1 In Server Admin, choose DNS in the Computer & Services list.
2 Click Settings.
3 Select the General tab.
4 Select or deselect Allow Recursion as needed.
If you choose to enable recursion, consider disabling it for external IP addresses, but
enabling it for LAN IP addresses, by editing BIND’s named.conf file. See BIND’s
documentation for more information.
Managing Zones
Zones are the basic organizational unit of the Domain Name System. Zones contain
records and are defined by how they acquire those records, and how they respond to
DNS requests. There are three kinds of zones:
Master
A master zone has the master copy of the zone’s records, and provides authoritative
answers to lookup requests.
Slave
A slave zone is a copy of a master zone stored on a slave or secondary name server.
Each slave zone keeps a list of masters that it contacts to receive updates to records in
the master zone. Slaves must be configured to request the copy of the master zone’s
data. Slave zones use zone transfers to get copies of the master zone data. Slave name
servers can take lookup requests like master servers. By using several slave zones linked
to one master, you can distribute DNS query loads across several computers and ensure
lookup requests are answered when the master name server is down.
Slave zones also have a refresh interval also. It determines how often slave zones check
for changes from the master zone. You can change the zone refresh interval by using
BIND’s configuration file. See BIND’s documentation for more information.
Forward
A forward zone directs all lookup requests for that zone to other DNS servers. Forward
zones don’t do zone transfers. Often, forward zone servers are used to provide DNS
services to a private network behind a firewall. In this case, the DNS server must have
access to the Internet and a DNS server outside the firewall.
Adding a Master Zone
A master zone has the master copy of the zone’s records and provides authoritative
answers to lookup requests. After adding a master zone, Server Admin automatically
creates an NS record with the same name as the Source of Authority (SOA).
LL2351.Book Page 22 Monday, September 8, 2003 2:47 PM