Paloalto Firewall and VPC peering

[crypto]

i am confuse AWS network firewall and peering section.
As per AWS documents, it said
**AWS Network Firewall cannot be deployed to inspect traffic between VPCs that are peered together; **

this mean AWS network firewall cannot support.

So let me know paloalto can support below scenario ?

i did vpc peering VPC 1 (10.1.1.0/16)and VPC2 ( 10.2.1.0/16).

VPC 1 have one private subnet ( 10.1.2.0/24) behind the PA firewall
VPC 2 have one private subnet ( 10.2.2.0/24) behind  the PA firewall
I have the one private route table destination 10.2.2.0/24 next hop is firewall interface in VPC 2.
I add one route to go 10.2.2.0/24 next hop is peer ID in VPC one private route.
I have the one private route table destination 10.1.2.0/24 next hop is firewall interface in VPC 1.
I add one route to go 10.1.2.0/24 next hop is peer ID in VPC 2.

let me know this traffic will pass firewall ?
can we use PA firewall to inspect traffic of private network(10.1.2.0/24 and 10.2.2.0/24) of  two vpc which it is peering?

I don't want to use transit gateway.

[sthornton]

Where are you planning to place the firewalls?

[crypto]

Hi @sthornton ,

Sorry for misunderstanding. I want to go VPC1 to VPC2 passthrough VPC3 PA firewall without using transit gateway and VPN.

[DanaHawkins]

This is a very odd setup. Why do you have a firewall in every VPC? By default subnet-2-subnet traffic within a VPC is not going to be inspected by the PA. it would be more practical to use VPC3 as the primary "Security VPC" inspecting traffic passing between VPCs.

With that said, your design CAN work but you would need a RouteTable in every subnet, please see below. I only included VPC1 and VPC3, you can duplicate the configuration for VPC2.

[DanaHawkins]

Another thing to keep in mind is that if you added more subnets within the VPCs you would need to consider the PA VM instance size. I believe you need a C4xLarge just to have the proper number of interfaces to place in each subnet. With more than 4 interfaces you would need to go to bigger instance size and it will start getting pricey.

[crypto]

Hi @DanaHawkins ,

When i read Doc, all are said need Transitgateway. I want to do VPC3 as security VPC and traffic VPC1 to VPC2 pass through VPC3 for inspection. is it possible without using Transit gateway ?

[DanaHawkins]

You achieve what you want with VPC peering using a design similar to the picture I posted above. Transit Gateways give you the benefit of Availability Zone redundancy and using BGP for route propagation between the firewalls and AWS. Using VPC peering all route table configurations are manual for both the firewall and AWS.

[sthornton]

I do not believe this is possible.  This would be transitive routing and would require an intermediary to accomplish.

[DanaHawkins]

The firewall is acting as the intermediary. VPC peer allows for connecting of resources between VPCs. @sthornton You are right that, if there was no firewall, or another intermediary, within the VPC then you would not be able to communicate from VPC1 to VPC2 via VPC3.

[dmaynard]

Unsupported VPC peering configurations

https://docs.aws.amazon.com/vpc/latest/peering/invalid-peering-configurations.html#transitive-peerin...

[DanaHawkins]

This would be true if you were only using AWS native constructs but introducing the Palo Alto FW in the "Transit" VPC would allow you to pass traffic/inspect traffic by sending traffic to a VPC subnet ENI resource to another subnet ENI resource. In effect, the Palo Alto FW becomes the "transit router" for the VPC.

VPCs as AWS native constructs are non-transitory in nature but a FW can act as the bridge.