Azure firewall rules processing logic

Venu Gopal Krishna VV 100

Hi All,

need some help in Azure firewall processing logic, i have two rule collection group in the application group as below.

i have google.com in both allow and deny action group. ideally lowest priority number will process fist, as shown below deny group has the highest priority and google.com shouldn't be allowed.

initially when this was implemented google.com was denied but all of a sudden, we are seeing google.com allowed though we have it mentioned in the deny action group. can someone please help on this. is there any change from Microsoft ? or am i missing something.

appreciate for help in this

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KapilAnanth-MSFT 41,491 Reputation points Microsoft Employee

2023-07-25T06:19:07.8333333+00:00
@Venu Gopal Krishna VV

Welcome to the Microsoft Q&A Platform. Thank you for reaching out & I hope you are doing well.

The only way to confirm this is to check which rule allowed the connection from Firewall logs.

Can you initiate traffic from a VM to google.com and make note of the time stamp.

And check Azure Firewall queries to see which rule allowed the traffic?

Cheers,

Kapil
Venu Gopal Krishna VV 100 Reputation points

2023-07-25T06:30:51.8766667+00:00

@KapilAnanth-MSFT

Allow group allowed the rule, ideally it shouldn't be allowed right ?

and is my logic of rule processing is correct ?

can you please help on this
KapilAnanth-MSFT 41,491 Reputation points Microsoft Employee

2023-07-25T06:33:48.3133333+00:00
@Venu Gopal Krishna VV

Can you please share the screenshot of Allow?

"logic of rule processing is correct ?"

Yes

Ideally, the traffic should be denied and rule processing should end there.

Cheers,

Kapil
Andreas Baumgarten 104K Reputation points MVP

2023-07-25T06:34:04.04+00:00

Hi @Venu Gopal Krishna VV ,

maybe this article is helpful to figure out the Azure Firewall processing order. Configure Azure Firewall rules

The processing order might be complex if different Rule Collection types are in use and combined.

(If the reply was helpful please don't forget to upvote and/or accept as answer, thank you)

Regards

Andreas Baumgarten
KapilAnanth-MSFT 41,491 Reputation points Microsoft Employee

2023-07-26T06:50:26.4866667+00:00

@Venu Gopal Krishna VV

May I know if you got a chance to review my previous comment?

Please let me know if you are facing any challenges or if there are any follow-up questions, I shall be glad to address them.

Thanks,

Kapil
KapilAnanth-MSFT 41,491 Reputation points Microsoft Employee

2023-07-27T06:12:56.47+00:00

@Venu Gopal Krishna VV

Can you please update us if the issue was resolved?

Should there be any follow-up questions or concerns, please let us know and we shall try to address them.

Thanks,

Kapil

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Azure firewall rules processing logic