Dynamic dns with BIND and Mikrotik

Tested on Centos 6.7

Assuming we have the domain name domain.com with private nameservers ns1.domain.com and ns2.domain.com that will resolve to 1.1.1.1 and 2.2.2.2 respectively.

We also have a VPS with static IP 1.1.1.1 on which we will setup dyndns server for Mikrotik clients.

Install BIND (version 9.8.2 in our case), PHP and the text editor:

yum install bind nano php

Add include directive:

nano /etc/named.conf

include "/var/www/html/dyndns/domain.com.zones";

Add the primary DNS zone:

        zone "domain.com" IN {
               type master;
               file "domain.com.zone";
               allow-update { none; };
       };

Save and close.

Create the primary zone file:

nano /var/named/domain.com.zone

$TTL 86400
@   IN  SOA     ns1.domain.com. root.domain.com. (
       2013042201  ;Serial
       3600        ;Refresh
       1800        ;Retry
       604800      ;Expire
       86400       ;Minimum TTL
)
; Specify our two nameservers
               IN      NS              ns1.domain.com.
               IN      NS              ns2.domain.com.
; Resolve nameserver hostnames to IP, replace with your two droplet IP addresses.
ns1             IN      A               1.1.1.1
ns2             IN      A               2.2.2.2

; Define hostname -> IP pairs which you wish to resolve
@               IN      A               1.1.1.1
www             IN      A               1.1.1.1

In our case 1.1.1.1 and 2.2.2.2 are the same IP. We have ns1 and ns2 at the same VPS.

Create and open zones file.

mkdir -p /var/www/html/dyndns
nano /var/www/html/dyndns/domain.com.zones

Insert zone for each dynamic host, for example:

       zone "dyn.domain.com" IN {
               type master;
               file "/var/www/html/dyndns/dyn.domain.com/dyn.domain.com.zone";
               allow-update { none; };
       };

Add dynamic subdomain

Assuming we have a running Apache webserver with default configuration and web root /var/www/html/.

Step 1 Create zone file.

mkdir /var/www/html/dyndns/dyn.domain.com
chmod root:apache /var/www/html/dyndns/dyn.domain.com
nano /var/www/html/dyndns/dyn.domain.com/dyn.domain.com.zone

$TTL 86400
@   IN  SOA     ns1.domain.com. root.domain.com. (
       2013042201  ;Serial
       3600        ;Refresh
       1800        ;Retry
       604800      ;Expire
       86400       ;Minimum TTL
)
; Specify our two nameservers
               IN      NS              ns1.domain.com.
               IN      NS              ns2.domain.com.
; Resolve nameserver hostnames to IP, replace with your two droplet IP addresses.
ns1             IN      A               1.1.1.1
ns2             IN      A               2.2.2.2

; Define hostname -> IP pairs which you wish to resolve
@ IN A 1.2.3.4

Where 1.1.1.1 and 2.2.2.2 are the IPs of nameservers and 1.2.3.4 is the IP of dynamic host.

Step 2 Create php script for receiving input from clients;

nano /var/www/html/dyndns/dyn.domain.com/deviceupdate.php

<?php
  $ip=$_SERVER[REMOTE_ADDR];
  if ($_GET['hash']="ae2b1fca515949e5d54fb22b8ed95575") {
    file_put_contents("deviceupdate.log","DATE: ".date("Y-m-d H:i:s")." IP: ".$ip."\n",FILE_APPEND | LOCK_EX);
    file_put_contents("homeip.log",$ip,LOCK_EX);
    print "DATE: ".date("Y-m-d H:i:s")." IP: ".$ip;
  }
?>

Step 3 Create bash script for updating BIND zones.

nano /var/www/html/dyndns/dyn.domain.com/dyndns.sh

#!/bin/bash
newip=$(cat /var/www/html/dyndns/vq1.vpsget.net/homeip.log)
md5old=$(cat /var/www/html/dyndns/vq1.vpsget.net/homeip.md5)
md5new=$(md5sum /var/www/html/dyndns/vq1.vpsget.net/homeip.log)

#echo "$(date) RunTime" >> /var/log/dyndns.log
if test "$md5old" = "$md5new"
then
       echo "$(date) - No change" >> /var/log/dyndns.log
else
       sed -i "/@ IN A/ c\@ IN A $newip" /var/www/html/dyndns/dyn.domain.com/dyn.domain.com.zone
       rndc reload dyn.domain.com
       md5sum /var/www/html/dyndns/dyn.domain.com/homeip.log > /var/www/html/dyndns/dyn.domain.com/homeip.md5
       echo "$(date) - Updated ip $newip" >> /var/log/dyndns.log
fi

Make it exacutable:

chmod +x /var/www/html/dyndns/dyn.domain.com/dyndns.sh

Step 4 Set a cron task:

nano /etc/crontab

*/5 * * * * root /var/www/html/dyndns/dyn.domain.com/dyndns.sh

Restart BIND:

service named restart

Client side.

In our case the client is Mikrotik router board.

Add the following script to Mikrotik and setup scheduler to run every few minutes.

/tool fetch keep-result=no mode=http url="http://domain.com/dyndns/dyn.domain.com/deviceupdate.php?hash=ae2b1fca515949e5d54fb22b8ed95575"