Suppose my institution wants to block all incoming HTTP and HTTPS requests, so firewall is configured for blocking access for incoming request to port 80 and 443, but I can configure some other port for my application for listening for HTTP service, let's say 7001. Then in this case how institution would be able to block?

1 Answer 1


That depends on your equipment and software. For instance, many Cisco devices can use NBAR to do deep packet inspection in order to identify upper layer protocols in use.

  • Could you please elaborate? Aug 16, 2015 at 21:36
  • This is highly dependent on the equipment and software. Different vendors have different solutions. NextGen firewalls do this, too. What you are asking is too broad to give you a specific answer. Basically, the inspection of the packets goes beyond the port number to the content of the packets. It may be that an HTTP header is seen in a packet in the stream to identify it as HTTP, and then appropriate action is taken, or not taken, depending on the rules.
    – Ron Maupin
    Aug 16, 2015 at 21:50
  • Oh I see, thanks, I don't think it could be better explained than this. Aug 16, 2015 at 21:56

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