Information Technology Reference
In-Depth Information
DNS data is called resource records (RR). Resource records are the data within a DNS
zone. Table 8-28 lists some common resource records.
Ta b l e 8 - 2 8
DNS Resource Records
DNS RR
Description
A
Address. Provides the name-to-address mapping. It contains the IP address in
dotted-decimal form.
AAAA
Secure IPv6 address.
CNAME
Canonical Name. Used for aliases or nicknames.
MX
Mail Exchanger. Specifies the IP of the server where mail should be delivered.
NS
Name Server. Specifies the name of the device that provides DNS for a particular
domain.
PTR
Pointer. Used for reverse mapping from the translation of IP addresses to names.
SOA
Start of Authority. Designates the start of a zone. This is the device that is the
master of DNS data for a zone.
DNS uses TCP and UDP port 53. UDP is the recommended transport protocol for DNS
queries. TCP is the recommended protocol for zone transfers between DNS servers. A
zone transfer occurs when you place a secondary server in the domain and transfer the
DNS information from the primary DNS server to the secondary server. A DNS query
searches for the IP address of an FQDN, such as
www.cnn.com
.
One important note for the CCDA to remember is to place DNS servers in the Enterprise
Campus Server Farm module and Enterprise Branch of the Enterprise Campus architec-
ture (see Figure 8-7).
Ta ble 8 - 2 9 summarizes the placement of DHCP and DNS servers on the Cisco enterprise
network.
Ta b l e 8 - 2 9
DHCP and DNS Servers
Network Location
Server Type
Campus Data Center
DHCP and Internal DNS
Enterprise Branch
DHCP and Internal DNS
E-Commerce
External DNS
Internet
External DNS
SP Edge Premises
Internal DNS
Remote Enterprise Data Center
Internal and External DNS
