Detailed Objective

Weight: 3

Description:
Candidates should be able to create a zone file for a forward or reverse zone or root level server. This objective includes setting appropriate values for records, adding hosts in zones and adding zones to the DNS. A candidate should also be able to delegate zones to another DNS server.

• Key knowledge area(s):
  • BIND 8.x and 9.x configuration files, terms and utilities
  • Utilities to request information from the DNS server
  • Layout, content and file location of the BIND zone files
  • Various methods to add a new host in the zone files, inlcuding reverse zones

• The following is a partial list of the used files, terms and utilities:
  • contents of /var/named/
  • zone file syntax
  • resource record formats
  • dig
  • nslookup
  • host

Create and maintain DNS zones

DNS zone files are composed mostly by resources records (RR) Resource records must start in the frst column of a line The order in which they appear is not important, but most people tend to follow the order in the DNS RFCs SOA (Start Of Authority) : indicates authority for this zone NS (NameServer) : lists a nameserver for this zone Other records :

A : name-to-address mapping PTR : address-to-name mapping CNAME (canonical name) : aliases Don't forget to create a zone for 127.0.0 ! Create and maintain DNS zones Usual zone file format :

$TTL <ttl value>
<domain name>. IN SOA <nameserver name>. <user.email>. (
<serial>;  serial number
<refresh>; refresh value
<retry>;  retry value
<expire>;  expire value
<n-ttl>;  negative caching TTL of 1 day
<domain name>.  IN  NS  <authoritative NS name>.
<domain name>.  IN  NS  <authoritative NS name>.
...
<hostname>.  IN  A  <IP address>
<hostname>.  IN  A  <IP address>
...

Create and maintain DNS zones For reverse mappings : $TTL <ttl value> <reverse net addr>.in-addr.arpa. IN SOA <NS name>. <user.email>. ( <serial>; serial number <refresh>; refresh value <retry>; retry value <expire>; expire value <n-ttl>; negative caching TTL of 1 day <rev net addr>.in-addr.arpa. IN NS <authoritative NS name>. <rev net addr>.in-addr.arpa. IN NS <authoritative NS name>. ... <rev IP addr>.in-addr.arpa. IN PTR <fqdn>. <rev IP addr>.in-addr.arpa. IN PTR <fqdn>. ...

Key terms, files and utilities : Content of /var/named Zone file syntax Resources record formats Dig Nslookup Host