I am currently configuring the DNS on Ubuntu servers for an assignment, and am encountering issues with reverse lookups. Below are the details from the configuration files and the results of the commands I've run:
p04ldns1.pod04.lan = master server [10.4.30.4]
- Can resolve
client1.pod04.lanto 10.4.30.10 - Can resolve
p04ldns2.pd04.lanto 10.4.30.5 - Cannot resolve 10.4.30.10 to
client1.pod04.lan - Cannot resolve 10.4.30.5 to
p04ldns2.pd04.lan
p04ldns2.pod04.lan = slave server [10.4.30.5]
- Can resolve
p04ldns1.pd04.lanto 10.4.30.4 - Cannot resolve
client1.pod04.lanto 10.4.30.10 - Cannot resolve 10.4.30.4 to
p04ldns1.pd04.lan - Cannot resolve 10.4.30.10 to
client1.pod04.lan
client1.pod04.lan = client [10.4.30.10]
- Can ping 10.4.30.4 & 10.4.30.5
- Can get out to the internet using 10.4.30.4 & 10.4.30.5 as DNS servers
Forward Lookup Zone Configuration on Master (/etc/bind/named.conf.local)
// Forward Lookup Zone zone "pod04.lan" { type master; // Confirmed as master file "/etc/bind/db.pod04.lan"; // Correct file path }; // Reverse Lookup Zone zone "30.4.10.in-addr.arpa" { type master; // Confirmed as master file "/etc/bind/30.4.10.in-addr.arpa"; // Correct file path }; Zone File for pod04.lan on Master (/etc/bind/db.pod04.lan)
$TTL 604800 $ORIGIN pod04.lan. @ IN SOA p04ldns1.pod04.lan. admin.pod04.lan. ( 2023100805 ; Serial 604800 ; Refresh 86400 ; Retry 2419200 ; Expire 604800 ) ; Negative Cache TTL ; @ IN NS p04ldns1.pod04.lan. @ IN NS p04ldns2.pod04.lan. p04ldns1 IN A 10.4.30.4 p04ldns2 IN A 10.4.30.5 client1 IN A 10.4.30.10 Zone File for Reverse Lookup on Master (/etc/bind/30.4.10.in-addr.arpa)
$TTL 604800 $ORIGIN 30.4.10.in-addr.arpa. @ IN SOA p04ldns1.pod04.lan. admin.pod04.lan. ( 2023100805 ; Serial 604800 ; Refresh 86400 ; Retry 2419200 ; Expire 604800 ) ; Negative Cache TTL ; @ IN NS p04ldns1.pod04.lan. @ IN NS p04ldns2.pod04.lan. 10 IN PTR client1.pod04.lan. Slave zone file The slave cannot resolve client1.pod04.lan to 10.4.30.10
// FORWARD LOOKUP ZONE zone "pod04.lan" { type slave; file "/var/cache/bind/db.pod04.lan"; masters { 10.4.30.4; }; # P04LDNS1's IP Address }; // REVERSE LOOKUP ZONE zone "30.4.10.in-addr.arpa" { type slave; file "/var/cache/bind/30.4.10.in-addr.arpa"; masters { 10.4.30.4; }; # P04LDNS1's IP Address }; I have set the permissions for the reverse zone file as follows:
sudo chown bind:bind /etc/bind/30.4.10.in-addr.arpa sudo chmod 644 /etc/bind/30.4.10.in-addr.arpa Testing Commands and Results
Forward Lookup:
dig @10.4.30.4 client1.pod04.lan Result: Successfully resolves to 10.4.30.10.
Reverse Lookup:
dig -x 10.4.30.10 Result: NXDOMAIN, indicating the reverse lookup is not resolving.
dig -x 10.4.30.10 @10.4.30.4 Result: Also returns NXDOMAIN.
sudo ufw status Status: active To Action From -- ------ ---- 22/tcp ALLOW Anywhere 53 ALLOW Anywhere 22/tcp (v6) ALLOW Anywhere (v6) 53 (v6) ALLOW Anywhere (v6) Have tried sudo systemctl restart bind9 many times on master and slave dns servers
dig @10.4.30.4 pod04.lan AXFR on SLAVE
; <<>> DiG 9.18.28-0ubuntu0.24.04.1-Ubuntu <<>> @10.4.30.4 pod04.lan AXFR ; (1 server found) ;; global options: +cmd pod04.lan. 604800 IN SOA p04ldns1.pod04.lan. admin.pod04.lan. 2023100805 604800 86400 2419200 604800 pod04.lan. 604800 IN NS p04ldns1.pod04.lan. pod04.lan. 604800 IN NS p04ldns2.pod04.lan. client1.pod04.lan. 604800 IN A 10.4.30.10 p04ldns1.pod04.lan. 604800 IN A 10.4.30.4 p04ldns2.pod04.lan. 604800 IN A 10.4.30.5 pod04.lan. 604800 IN SOA p04ldns1.pod04.lan. admin.pod04.lan. 2023100805 60480 
