Azure Firewall behind public load balancer configuration

[jameswonderguy]

Hi,

I have a requirement to replace Sophos firewall with Azure Firewall Premium. The existing Sophos firewall is behind a public Azure load balancer (backend pool comprises the Sophos Firewall IPs).

To set up a parallel configuration for Azure Firewall, I have configured a new public IP on the load balancer's frontend IP configuration. However, I do not see the Azure Firewall's public IP when trying to configure a backend pool. All the listed IPs belong to the same subnet as the load balancer's internal IP. 

As per the below article, one can configure firewalls behind an external load balancer.

https://learn.microsoft.com/en-us/azure/architecture/example-scenario/firewalls/

I am trying to understand how to chain the public load balancer and Azure firewall such that I can access internal resources as is currently being done with the same public load balancer and Sophos firewall (NIC of Sophos is in the same subnet as internal NIC of this load balancer).

Can someone please guide me?

Thanks

James

[#2]

@jameswonderguythis is not a valid config and it does not make any sense to be honest. You can't put Azure firewall in LB backend pool and you can only add private IPs or NICs from the same LB VNET to the backend pool.

Why would you want to put the firewall behind a load balancer in the first place? The FW has a public front end IP that you can use for incoming traffic from internet and and a private IP for the traffic coming from the local VNET or peered VNETs. There is no need for the load balancer at all.

[#3]

@anas86, Thank you for your response! I was able to set up the Azure Firewall to accept incoming and outgoing traffic.