Port 53 is reserved for the Domain Name System (DNS). In your case it is the DNS cacher dnsmasq of the package dnsmasq-base. This pre-installed package is a dependency of network-manager, the network manager of your desktop environment (e.g. Unity, GNOME, …). For this reason, don't uninstall the package dnsmasq-base and/or disable the service.
In another well-known case, versions of the Zone Alarm personal firewall up to 2.1.25 allowed any incoming UDP packets with the source port 53 (DNS) or 67 (DHCP). A 2005 answer in Seclists.org provides a quote from a previous version of the Reference Guide:--source_port
Jul 13, 2005
iptables - Opening port 53 on server Risks? - Information Opening port 53 on server Risks? Ask Question Asked 5 years, 3 months ago. Active 5 years, 3 months ago. Viewed 5k times 0. 2. I looked about but couldn't find a similar enough question. I have some remote servers positioned on clients networks, which provide various services (raspberry pi) - and their firewall config is as follows: Only
Oct 10, 2018
Port 53 is reserved for the Domain Name System (DNS). In your case it is the DNS cacher dnsmasq of the package dnsmasq-base.This pre-installed package is a dependency of network-manager, the network manager of your desktop environment (e.g. Unity, GNOME, …).. For this reason, don't uninstall the package dnsmasq-base and/or disable the service. Install bind9 and all is fine telnet to port 53 - Cisco Community telnet to port 53 If you are trying to see if connectivity works on DNS request (normally uses UDP/53), then the answer is no, telnet on port 53 will not work. If you are trying to test DNS resolution/request, then just use "nslookup" from command prompt, then specify the dns server: server , … Port 53 Restaurant Restaurant Info and Reservations