Scenario / Question: IPTables is blocking DNS and I can not get DNS from Internet. Solution / Answer: IPTables needs to be configured to allow INPUT of port 53 and the OUTPUT of port 53. DNS uses both tcp and udp protocols on port 53 for communicating. UDP is used for queries transferring less [continue...]

Scenario / Question: How do I find out what service is associated with what port. For example how can I find out what port secure pop3 (pop3s) uses? Solution / Answer: In Redhat based systems there is a file called /etc/services that contains a directory of well known services and their ports. [continue...]