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Ask the Expert- SD-WAN


NGFW Policy Order of Operations

After reading the NGFW Policy Order of Operations guide here,

I am even more confused about how the firepower device processes rules. According to this guide, if I want to block all port 443, but allow access to google drive, I would need to put a rule blocking 443 before the rule allowing google drive. This is on page 5 of the linked guide.


Could someone please explain how a setup like that would allow google drive while simultaneously blocking all 443 traffic? If the block for port 443 comes before the application detection rule for google drive, the application detection rule would never be able to identify a google drive connection, because it would be blocked at the very first packet.


Everyone's tags (1)

Re: NGFW Policy Order of Operations

So to briefly hit on the order of operation Security Intelligence will occur first prior to parsing through your access control entries, which is where you can do global whitelisting/blacklisting. After that your mandatory rules will be evaluated followed by the remaining zones and ACEs in an ordered fashion. As for your use case you have a couple of options. You could accomplish it using URL filtering in an ACE, application filtering in an ACE, whitelisting, or straight up old school IP to IP and then block all on port 443.

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Re: NGFW Policy Order of Operations

Thanks Mike,


I think I understand the order of operations, but I'm trying to figure out if there is a discrepancy in the guide I'm reading, since it it proposing to make a 443 blacklist ACE in the ACP before the application detection ACE for allowing google drive.


It would seem to me that such a configuration would not properly allow google drive to work, since all 443 traffic would be blocked prior to the google drive allow - e.g. the application detection would not be able to do it's job because the 443 block ACE is preventing any packets from getting through. However the cisco published guide is clearly stating this is the preferred way to set up such a configuration.


Assuming you were in some ultra-high security environment where you were doing zero trust and whitelisting, blocking 443 at the top of the ACL would render any application detection useless, correct?

Cisco Employee

Re: NGFW Policy Order of Operations

That example scenario just covers a specific scenario when blocking ALL traffic to port 443 is required. It specifically says on page 5: 'If we want to block ALL traffic going to Port 443 we want to ensure this rule is NOT below a rule containing an Application Filter or something we will need to wait for information for". This means that IF the intention is to block ALL traffic going to port 443, then rules 3 should be 1st in the list.
In other scenarious implementation may be different.