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visits member for 2 years, 11 months
seen Mar 20 at 16:30

linux, python, floss, trading


Sep
24
awarded  Autobiographer
Feb
21
awarded  Citizen Patrol
Feb
21
comment When would I open Port 53 for DNS?
Gentlemen, this argument via comments is pointless. Michael Hampton, indeed, but the practice of allowing client/server communication via the same privileged port (0-1023) has been stopped by Iana RFCs. @Shane I am not talking about theoretical possibilities, but practical reality: the OP is "Locking down an application server" and has tagged it "linux". If you want to disprove my assertion then prove it wrong via a source or command line output. I have work to do and will not engage in further talk.
Feb
21
comment When would I open Port 53 for DNS?
Condescension doesn't change the fact that the OP is referring to a Linux host. A note on your answer doesn't change the fact that the TCP/IP model (of which UDP is a subset) does not allow common services (like DNS) to communicate over the same port. Your answer statement "You need to have UDP 53 allowed for responses to DNS queries that your server sends, as UDP is a stateless protocol. Don't block it if you want any kind of outbound connectivity, software updates, etc." is wrong.
Feb
21
comment When would I open Port 53 for DNS?
Look man, you're talking a lot but the answer to the question remains that you only need port 53 open on a host that serves DNS to the network. Execute 'tcpdump -n -s 1500 -i eth0 udp port 53' to confirm that a client DNS request never uses port 53 on the localhost
Feb
21
awarded  Critic
Feb
21
comment When would I open Port 53 for DNS?
i politely but totally disagree with the stated need for port 53 to be open to external hosts in order for the localhost to resolve DNS. I am writing this message from a machine with port 53 closed. TCP connection tracking on the (localhost) firewall manages the authenticity of DNS queries going out from random ports above port 1023.
Feb
21
revised When would I open Port 53 for DNS?
tcpdump code
Feb
21
comment When would I open Port 53 for DNS?
the belief that outbound DNS queries use port 53 is incorrect.
Feb
21
answered When would I open Port 53 for DNS?
Dec
31
answered Where to see logs of a program that crashes on Ubuntu Server?
Dec
27
awarded  Supporter
Dec
26
answered Restrict User Access to Certain Ports
Dec
25
awarded  Editor
Dec
25
revised Firewalling tool for VirtualBox
formatting to emphasize critical terms
Dec
25
awarded  Teacher
Dec
25
answered Firewalling tool for VirtualBox