Application and services in security policy rules

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Application and services in security policy rules

L1 Bithead

Hi I have a question,




Following rule,


Application allowed- DNS,SSL,WEB-Browsing


Service allowed - TCP port 22



I understand DNS, SSL and Web-browsing would be allowed on port 22, but my question is SSH  traffic  would be allowed by this rule as I am allowing port-22 via service.?


Also My second question, would DNS traffic  be allowed on its standard  port 53 via this rule?



My understanding is Palo matches Both Services and Application together, hence SSH traffic would be blocked in this case and DNS traffic on port 53 would  also be blocked?


Referring this article -




Cyber Elite
Cyber Elite

The service configuration limits which ports the applications are allowed to use

Setting tcp-22 in the services limits ALL applications to only be allowed through tcp:22 (so DNS will need to use TCP 22 instead of UDP 53)


if DNS needs to be allowed too, you'll need to add udp53 to the services



Tom Piens
PANgurus - Strata specialist; config reviews, policy optimization

Cyber Elite
Cyber Elite


While there maybe a reason for restricting the application traffic, I would break these out into their own separate policies. This way you have tighter control over applications and which ports they can/should use.



Hi Reaper,

That makes sense but just confirming SSH traffic will also be blocked in the case as I have not allowed SSH in application section?


Please confirm

L2 Linker

break application  out into their own separate security policies and define whatever port you desire to use except you want all the app on the same port 22 and also define udp port.

Simplicity is the friend of Security, whilst complexity is the Enemy. (Bruce Schneier) PCNSE,CCSA, SEC-Plus, CCNA Security


Correct, you will need to have ssh in the application field to allow the traffic. You will not need a 'service'/port since that is implied in the application.




It would be nice if you could get away with an "and"  for app default- AND any port you specify in the rule. 

Cyber Elite
Cyber Elite


You absolutely can. However the point with the applications is that you dont have to. So instead of a policy that is like:

application = ssh and service = 22/tcp, you can just put in application = ssh.


Thats really it. The firewall knows and can see ssh and knows its only allowed on port 22/tcp by default.


Hope that helps.

I was under the impression that one rule was either app-default OR you pick the service.


app-default OR tcp/22  

So that means.

Lets says I allowed 5 applications in my rule 1 with "application-default"

The traffic from that rule would be allowed on all standard ports.


Now I have another non standard port to allow.

So I have to make another rule and allow ALL apps on that TCP- NON-STANDARD  port.


Does'it not open up all application traffic on that port.


Would'nt it be better if I use the non standard port in same rule 1 and somehow palo allows my 5 applications on their standard ports and also the non standard I added in services section.


That way I can have the traffic going to non standard port allowed and also applications to standard ports allowed in same rule.


That poses less secuirty risk rather than allowing all apps on that non standard port in a new rule?


@OtakarKlier @reaper

Cyber Elite
Cyber Elite


Let me try this: Lets say you want to allow the following applications:

ssl, web-browsing, and dns and dont put in any service/ports. The firewall will allow traffic that is sees as DNS only on port 53, web-browsing only on port 80 and ssl only on port 443. If DNS tries to use any other port, it will be blocked.

if you put in a policy that allows applications: ssl, web-browsing, and dns and ports 53, 80, 443. Then the firewall will allow any of those applications over any of those ports, ie DNS over 443, 80, 53.


So by not using a specific service/port, you are making your security policy that much stronger. If you want to allow an application say DNS over port 443, you will need to have a special policy that allows that. The firewall reads policies top down, left to right. Once it finds a match, thats what it will use.


Hope that makes sense. 

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