In our previous guide we covered the setup of Master(Primary) DNS Server. Here we’ll learn that how to configure slave bind dns server on Ubuntu 20.04 . As the name defined, slave obtains the data from the master & keeps this data in the zones for particular time & from there response to the DNS queries. So, let’s move towards the installation process.
Setup
Master DNS Server IP: 172.16.10.2
Master domain name:ns1.osradar.local
Slave DNS Server IP:172.16.10.10
Slave domain name:ns2.osradar.local
Step 1: Configure Master DNS Server On Ubuntu 20.04
The configuration procedure of slave DNS server is similar to the Master server. The main difference b/w is that slave gets it’s data from the Master DNS.
Edit the /etc/bind/named.conf.local file on primary server & add the allow-transfer & also-notify commands. Add this to both zones (forward & reverse).
sudo nano /etc/bind/named.conf.local
##Forward zone
zone "osradar.local" IN { // Domain name
type master; // Primary DNS
file "/etc/bind/forward.osradar.local.db"; // Forward lookup file
allow-update { none; }; // Since this is the primary DNS, it should be none.
allow-transfer { 172.16.10.10; }; //Allow Transfer of zone from the master server
also-notify { 172.16.10.10; }; //Notify slave for zone changes
};
##Reverse zone
zone "10.16.172.in-addr.arpa" IN { //Reverse lookup name, should match your network in reverse order
type master; // Primary DNS
file "/etc/bind/reverse.osradar.local.db"; //Reverse lookup file
allow-update { none; }; //Since this is the primary DNS, it should be none.
allow-transfer { 172.16.10.10; }; //Allow Transfer of zone from the master server
also-notify { 172.16.10.10; }; //Notify slave for zone changes
};
allow-transfer will help you to transfer data from Primary to secondary server.
also-notify helps you to notify the slave when update is available.
And after making these changes, restart the bind services.
sudo systemctl restart bind9
Step 2: Configure Slave DNS Server On Ubuntu 20.04
Install the following packages required for slave DNS server by typing
sudo apt-get install -y bind9 bind9utils bind9-doc dnsutils
Once packages are installed, edit the /etc/bind/named.conf.local file & update the forward & reverse DNS records.
sudo nano /etc/bind/named.conf.local
##Forward Zone
zone "osradar.local" IN { //Domain name
type slave; //Secondary Slave DNS
file "/var/cache/bind/forward.osradar.local.db"; //Forward Zone Cache file
masters { 172.16.10.2; }; //Master Server IP
};
##Reverse zone
zone "10.16.172.in-addr.arpa" IN { //Reverse lookup name. Should match your network in reverse order
type slave; // Secondary/Slave DNS
file "/var/cache/bind/reverse.osradar.local.db"; //Reverse Zone Cache file
masters { 172.16.10.2; }; //Master Server IP
};
And then restart the DNS services on slave.
sudo systemctl restart bind9
Step 3: Testing Slave DNS Server On Ubuntu 20.04
In order to test the working of slave DNS server, create a client machine on the slave server and hit.
sudo echo "nameserver 172.16.10.10" >> /etc/resolv.conf
Finally use the dig command to verify the DNS.
root@ubuntu20:~# dig www.osradar.local ; <<>> DiG 9.16.1-Ubuntu <<>> www.osradar.local ;; global options: +cmd ;; Got answer: ;; WARNING: .local is reserved for Multicast DNS ;; You are currently testing what happens when an mDNS query is leaked to DNS ;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 24401 ;; flags: qr aa rd ra; QUERY: 1, ANSWER: 1, AUTHORITY: 0, ADDITIONAL: 1 ;; OPT PSEUDOSECTION: ; EDNS: version: 0, flags:; udp: 4096 ; COOKIE: b1e287dd1d118ad6010000005f8c88233ef562a7063e7a15 (good) ;; QUESTION SECTION: ;www.osradar.local. IN A ;; ANSWER SECTION: www.osradar.local. 604800 IN A 172.16.10.3 ;; Query time: 0 msec ;; SERVER: 172.16.10.10#53(172.16.10.10) ;; WHEN: Sat Nov 18 18:23:31 UTC 2020 ;; MSG SIZE rcvd: 100
So, this is how you can configure DNS Slave Server on Ubuntu 20.04
