Introduction

This lab provides you with the instructions and practical experience to configure a name server as a primary master for a zone. Add the appropriate zone statement to the name servers named.conf file. The zone statement specifies the domain name of the zone and the name of the zone data file and that this name server is the zone's primary master.

You must also create the zone"s data file, which contains all of the resource records in the zone, including the SOA record and NS records.

                zone "bar.example" {
                    type master;
                    file "bar.example";
                    allow-transfer { 10.100.1.34; };
                };

              

• The most basic DNS lookup tool, is called host, if you run host www.mohawkcollege.ca it will return the ip address(es) of the website [A Records]
• The host command also works in reverse, if you run host 142.222.6.1 it will return the name(s) associated with that IP address [PTR records]
• There are more advanced DNS query tools, such as dig, this command returns more verbose output, as well as any additional records such as the NS records
• If we wanted to know which servers control mail for mohawkcollege, we could run: dig mohawkcollege.ca MX
• Other valid record types you can query with the dig tool are: A, AAAA, ANY, CNAME, MX, NS, PTR, SOA, SRV, and TXT (See the handbook for definitions)
• Dig also allows you to specify a non-default DNS server to use for your query, instead of reading /etc/resolv.conf, to do this: dig @142.222.125.21 name TYPE

Configuring a Name Server as a Primary Master

• A work around for the dhcp server overwriting  your /etc/resolv.conf file
• add the line prepend domain-name-servers 127.0.0.1;  to the /etc/dhclient.conf file
• /etc/rc.d/netif restart (to restart the network interface and dhclient)
  
• Edit /etc/resolv.conf and set your nameserver to 127.0.0.1
  
• Enable "named" in /etc/rc.conf (you do need this entry)
  
• The first time you start named, use the command: /etc/rc.d/named forcestart
• Any time after this, we can use the regular "start" and "stop" commands
• Every time you change a config file, or a zone file (later) you must do: /etc/rc.d/named reload
  
• The configuration directory for bind is /etc/namedb, and the main config file is named.conf
  
• Edit the BIND config file, (named.conf)  and change the following settings in the options block:  "forwarder" setting to 10.100.1.150
• The listen-on option must also be set in the option block to define which network interface your nameserver listens on for queries.  You could set this to any or to your local network.
  
• Continuing to edit the config file, and using the examples for a master forward and reverse zones, change the entries to reflect your your_domain.csait.ca as your zone.  The filename should be meaningful and reflect the name of the zone that you are authoritative for.
• The primary master name server must create the zone data files for forward and reverse mappings for your  domain (zone).
  
• You can use a copy of the zone files (under the master subdirectory) as an example and edit appropriately.
  
• Edit your new forward zone file and add an NS record for your nameserver and any "A" records to establish your zone.
  
• You will also need a zone datafile for reverse lookups.  Add the necessary PTR records for the hosts in your zone.  Use the sample configuration files for example resource records.
  
• Before restarting or reloading your database,  run tail -f /var/log/messages and tcpdump to watch for any errors.
• The other hosts in your row will want to point to your nameserver for name resolution. They must edit their resolv.conf file.
• Test that your nameserver is answering queries.  First check for an "A" record (from one of your hosts), check for a NS record
  
• Configure one of the hosts in your domain to act as a slave (secondary).
• Configure the  allow-transfer setting to the IP address of any slave that will be requesting a transfer of your zone files
• Use tcpdump to confirm that a zone transfer has completed successfully to your secondary
• Now make a change in your forward and reverse zone file to add a CNAME for one of your hosts, to point to WWW and a new host.
  
• Use  a query tool to confirm this change has taken effect.  Has it?  Did you change the serial number in the forward and reverse zone file?
  
• Next, configure your primary master nameserver to act as a secondary for the next row's domain. 
• To allow a slave name server to transfer zone files the allow-transfer sub statement  in named.conf can be used to control which slaves are allowed to transfer zone files.  This allow-transfer statement can be in the options section to apply to all zones or in the zone statement.
  

Testing DNS:

• Run tcpdump -n -p -s0 in another terminal while doing some lookups (man tcpdump for explainations of switches)
• Using dig or host, query your nameserver for hosts in your domain.