linux - When would I open Port 53 for DNS? - Server Fault
An "open port" means that the port is externally visible to clients in the network (or out on the internet, possibly). Contrary to popular belief a server or host does not need to have port 53 open to make outgoing DNS queries - this is not how the TCP/IP model works. You can run tcpdump on a host and then issue a DNS lookup from another ...
iptables - how to monitor traffic at port 53 (DNS) - Server Fault
2011年3月6日 · You can use this command: tcpdump -n -s 1500 -i eth0 udp port 53 (Replace 'eth0' with the name of your ethernet interface, e.g. 'fxp0') This shows all packets going in and out of your machine for UDP port 53 (DNS) Source:DNS exercise 1
internal dns - dnsmasq: failed to create listening socket for port 53 ...
2015年5月30日 · Check for port usage with; lsof -i -n -P In my case, systemd-resolved was blocking port 53 from use as below: systemd-r 640 systemd-resolve 12u IPv4 22295 0t0 UDP 127.0.0.53:53 systemd-r 640 systemd-resolve 13u IPv4 22296 0t0 TCP 127.0.0.53:53 (LISTEN) Simply disable systemd-resolved before enabling dnsmasq;
domain name system - how to open port 53 for bind - Server Fault
2010年2月8日 · port 53 isnt blocked by iptables. Share. Improve this answer. Follow edited Jan 28, 2015 at 16:19. iharob ...
Solved: deny all traffic to 53 from outside - Cisco Community
2012年10月5日 · I've deleted nat forwarding of port 53 to dummy address... now when I do portscan from outside.. 53 seems closed. Here is config: ip access-list extended INTERNET-IN. permit tcp any host MY_STATIC_OUTSIDE_IP eq 22. permit tcp any host MY_STATIC_OUTSIDE_IP eq 80. permit tcp any host MY_STATIC_OUTSIDE_IP eq 443. …
Do DNS queries always travel over UDP? - Server Fault
Normal DNS queries use UDP port 53, but longer queries (> 512 octets) will receive a 'truncated' reply, that results in a TCP 53 conversation to facilitate sending/receiving the entire query. Also, the DNS server binds to port 53, but the query itself originates on a random high-numbered port (49152 or above) sent to port 53.
telnet to port 53 - Cisco Community
2012年6月25日 · 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 , then test the resolution: cisco.com. Example from DOS prompt:
Locking down port 53 for Outbound Traffic - Cisco Community
2013年11月8日 · access-list LAN-IN permit udp any object-group INTERNAL-DNS-SERVERS eq 53. access-list LAN-IN permit tcp any object-group INTERNAL-DNS-SERVERS eq 53. access-list LAN-IN remark Block all other DNS traffic. access-list LAN-IN deny udp any any eq 53. access-list LAN-IN deny tcp any any eq 53. access-list LAN-IN remark Other firewall rules
Understanding how Unbound listen on Port 53 - Server Fault
2022年4月29日 · To prevent port hijacking, all of the processes binding to the same address must have the same effective UID. This option can be employed with both TCP and UDP sockets. For TCP sockets, this option allows accept(2) load distribution in a multi-threaded server to be improved by using a distinct listener socket for each thread.
Bind9 timeout from LAN, server listening on port 53
Previous versions of BIND always asked // questions using port 53, but BIND 8.1 and later use an unprivileged // port by default. // query-source address * port 53; // If your ISP provided one or more IP addresses for stable // nameservers, you probably want to use them as forwarders.