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Azure Firewall has no capacity to maintain source IP on outbound traffic?
Hello all, My use case: To have multiple static public IP addresses attached to Azure Firewall with SNAT rules configured so that the public IP isn't just randomly selected. We have multiple services that have whitelisting configured for specific public load balancer IPs and now we are trying to move them behind Azure Firewall. Since there is whitelisting on the destination, the public IP being randomly selected won't work. My resources: One instance of premium SKU Azure Firewall. Hub and spoke architecture. Route tables being used to force traffic through Firewall (routed to private IP of firewall) The research I have conducted: I have tried absolutely everything I can think of before coming to this forum and from what I can tell the 4 ways of outbound connectivity provided by Azure are: Default outbound connectivity. Against best practice to do this and won't work since its routing through a virtual appliance (firewall) Associate a NAT gateway to a subnet. This won't work since we have only one instance of Azure Firewall and the requirement for multiple public IPs to be used. Assign a public IP to a virtual machine. Not applicable, sitting in backend pool of a load balancer, single public IP to be used for multiple member servers. Using the frontend IP address(es) of a load balancer for outbound via outbound rules. Needs to go through the firewall, impossible unless we can somehow integrate the firewall between the load balancer and the backend pool? Expanding more on the load balancer scenario, I ran across this documentation in Microsoft Learn. This looks great to tackle the asymmetric routing issue, however, we are only interested in maintaining the source IP for outbound traffic, this would again just use the firewalls public IP for outbound traffic and again randomly select it. Consensus: It seems bizarre to me that Azure has no capacity for static SNAT configuration like most firewalls do. I would have thought a large amount of use cases would require this function. Am I missing something? Is there another workaround? Or is Azure just behind the 8ball with networking. Thanks heaps in advance for any help :) Much Appreciated, usernameone101
NAT GW operation
In a course, the below image is used to illustrate the operation of NAT GW. What I don't understand here is how asymmetric traffic is avoided. If an Azure resource is accessed over its associated public IP and the response comes back via the NAT GW performing SNAT using a different IP address, then most probably this traffic would be dropped by any well-behaving source entity. For instance, assuming HTTP traffic, I can't imagine a TCP session established like that. How does this work ?
