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Figure 5-9: Network Services
5.3.1 DNS
"DNS" stands for Domain Name System. DNS converts machine names to the IP addresses that all
machines on the net have. It translates from name to address and from address to name.
There are two kinds of domain name servers: one is the primary domain name server; the other is
the secondary domain name server. Each domain name needs a primary domain name server to
keep track of all the names on the domain, and some secondary domain name servers to act as
backup servers for the information on the primary domain name server. Information is configurable
only on the primary domain name server; secondary domain name servers only hold a copy of the
information on the primary domain name server, and are not configurable.
The primary domain name server has three configurable records: the A/PTR record, the MX record and
the CNAME record. The A/PTR is automatically divided into an Address record and PTR record once the
A/PTR record is created. The four kinds of records together make up all of the names in a domain.
Also, there is a Start of Authority (SOA record), which contains the domain's primary name server,
its secondary name server, the domain administrator's email address, and some additional
parameters that are set by the ISA-4000.
The definitions of the three configurable records are as follows:
•
A/PTR record:
this is a name-to-address mapping record; the ISA-4000 automatically
reverses it to an address-to-name mapping (this record is also called a PTR [Pointer
Record]). A/PTR records contain all of the qualified names in the domain.
•
CNAME record:
this is an alias to another name in the forward record; the alias should map
to a real name that exists in a forward record.
•
MX record:
this is a mail server name in the domain.
5 . 3 . 1 . 1 E
N A B L I N G T H E
D
O M A I N
N
A M E
S
E R V E R
1. Click
Network Services
.
2. Click
DNS
.
3. Check Enable DNS Server:
