check DNS ports accessible with nmap

# Subject: example of checking port accessibility for 53/tcp and 53/udp to confirm nameserver active
# Date: Sun  6 Oct 18:48:39 BST 2024

Introduction:

Example of how to check for active DNS ports 53/tcp and 53/udp on nameserver using nmap


Commands:

my_bind_nameserver_IP_address=192.168.1.53  ##LOCAL change this to your nameserver's IP address

nmap -Pn -p53 ${my_bind_nameserver_IP_address}  # test if 53/tcp accessible

/bin/sudo nmap -Pn -p53 -sU ${my_bind_nameserver_IP_address}  # test if 53/udp accessible



Example:


[user@localhost ~]$ my_bind_nameserver_IP_address=192.168.1.53  ##LOCAL change this to your nameserver's IP address

[user@localhost ~]$ nmap -Pn -p53 ${my_bind_nameserver_IP_address}  # test if 53/tcp accessible
Starting Nmap 7.95 ( https://nmap.org ) at 2024-10-06 18:35 BST
Nmap scan report for nameserver.home (192.168.1.53)
Host is up (0.00030s latency).

PORT   STATE SERVICE
53/tcp open  domain

Nmap done: 1 IP address (1 host up) scanned in 0.04 seconds

[user@localhost ~]$ /bin/sudo nmap -Pn -p53 -sU ${my_bind_nameserver_IP_address}  # test if 53/udp accessible
Starting Nmap 7.95 ( https://nmap.org ) at 2024-10-06 18:35 BST
Nmap scan report for nameserver.home (192.168.1.53)
Host is up (0.00018s latency).

PORT   STATE SERVICE
53/udp open  domain
MAC Address: 00:1A:6B:4D:C5:35 (Universal Global Scientific Industrial)

Nmap done: 1 IP address (1 host up) scanned in 0.41 seconds