Hello Team,
I have a dedicated server and in there, I have installed plesk. The issue is, all the listening ports can be connected except UDP port 53.
[root@server ~]# netstat -nlup | grep 53
udp 0 0 1.2.3.4:53 0.0.0.0:* 1164/named
udp 0 0 127.0.0.1:53 0.0.0.0:* 1164/named
> From my PC,
sudo nmap -p 53 -sU 1.2.3.4
Starting Nmap 7.94 ( https://nmap.org ) at 2023-06-06 11:13 +0545
Nmap scan report for server.abcxyz.com (1.2.3.4)
Host is up (0.17s latency).
PORT STATE SERVICE
53/udp open|filtered domain
Nmap done: 1 IP address (1 host up) scanned in 2.49 seconds
> Its almalinux 8:
- csf/ldf disabled
- iptables stopped
- firewalld stopped
- selinux disabled
> If I go inside the server and do dig locally, resolution works
> recursion allowed for any
> name-chroot is working instead of named.
> with tcpdump test, interface not receiving any UDP 53 packets
To my surprise, except port 53, everything else is listening. I did open random ports using netcat as well and they are working. What is up with this particular port. Somebody, please share insight if you have.
Thank you