Azure Portal - Add DNAT firewall rule error

Lord Saradomin 0

"Cannot read properties of undefined (reading 'toLowerCase')"

Get the above error when clicking 'Add rule' in the DNAT rules blade under our Firewall policy.

Rohith Vinnakota 3,160 Reputation points Microsoft External Staff

2025-03-11T19:03:02.3366667+00:00
Hi @Lord Saradomin

Could you please follow these steps to resolve the error "Cannot read properties of undefined (reading 'toLowerCase')" when adding a DNAT rule in Azure Firewall Policy:

Try using a different browser to see if the error persists.

Ensure all mandatory fields are filled and valid.

Make sure the rule name does not contain any special characters or spaces.

Open your browser’s developer tools, reproduce the error, and check for detailed error messages. Look for the exact line of code causing the failure and any missing data properties (e.g., undefined values in API responses).

If the issue still persists, please share screenshots of the values you are adding to the DNAT rule, the error message, and browser console logs in the private messages, so we can check and guide you accordingly.
Rohith Vinnakota 3,160 Reputation points Microsoft External Staff

2025-03-12T19:57:55.18+00:00

Hello @Lord Saradomin

Following up to see if the above suggestion was helpful. And, if you have any further query do let us know.

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