Revision 1
DNS
Records in a zone
• Zones consist of a number of records
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A records – host records in IPv4
AAAA records – host records in IPv6
PTR (pointer) records resolve an IP in to a hostname
CName (canonical name) – alias of one name to another
MX record – mail exchange record to locate mailservers
NS record – identifies nameservers for a domain
SOA – start of authority specifies information about the zone
Getting record information
dig is used to query domain name servers
Eg : dig bangor.ac.uk
Getting specific record types
• Pass the record type to dig
• Eg : dig bangor.ac.uk MX
Reverse lookup
• Use the option –x
Linux Nameservers
• Use the package bind
• Configuration file is /etc/named.conf
• Listens on port 53 (UDP)
• Zones are referenced in named.conf
Creating a new zone
• Add the zone to named.conf
Reverse resolution zones
Similar to forward resolution statement
Blocks of the IP address are reversed
.in-addr.arpa is included after them
zone “1.0.10.in-addr.arpa” IN {
type master;
file “domain.com.rr.zone”;
allow-update {none;};
};
• PTR records in zone file
<last IP digit>
• 20
IN
IN
PTR
PTR <FQDN of system>
dev.mydomain.com.
