In this lecture, we'll be talking about three of the most common deployments for AWS Network Firewall: distributed, centralized, and combined distributed and centralized. The first deployment model is the distributed type. This is where an AWS Network Firewall is deployed into each individual VPC. In most cases, AWS Network Firewall would only be deployed into each VPC that requires protection. Take note that each VPC does not require connectivity to others or even an AWS transit gateway for communication. Each AWS Network Firewall will have its own firewall policy or shared policy, which is a common set of rules, and will be managed independently. 

This might seem like a lot of overhead, but it also limits the possibility of any misconfigurations and impacts. Does this mean if you have 50 VPCs an AWS Network Firewall needs to be deployed into each? Yes. Which brings me to the next deployment option, centralized. If you're looking to centralize your AWS Network Firewall deployment, and which all network traffic is routed into one VPC which is typically used as a central way to inspect VPC traffic, then a central deployment model is the way to go. Take note that you need to have an AWS Transit Gateway set up and configured as a prerequisite. This acts as a network hub to provide connectivity between VPCs and on-premise network. 

For more information on AWS Transit Gateway, please see our existing course here. The last deployment model does a combination of both, where the AWS Network Firewall is deployed as a distributed and centralized. You can deploy into a centralized VPC to inspect VPC traffic, in which all Internet flows through this VPC, as well as deploy the AWS Network Firewall into individual VPCs. How about we take a look and compare the different deployment models and what is or isn't supported? First, let's talk about east-to-west or VPC to VPC traffic flow. It's not supported for a distributed AWS Network Firewall deployment model, but it is supported for centralized deployment model and a combination which supports a centralized. How about north-to-south, VPC to Internet traffic

flow? For distributed, supported, centralized, supported, and a combined AWS Network Firewall deployment model, supported. What about north-to-south, VPC to on-premise, via a VPN or a direct connect traffic flow? Distributed AWS Network Firewall deployment model is not supported, but the other two are between centralized and a combination of both. What are some of the prerequisites? For distributed, an AWS Network Firewall subnet. For centralized, inspection VPC and AWS Transit Gateway, and a combined AWS Network Firewall deployment model, a network firewall subnet in each VPC, an inspection VPC, and an AWS Transit Gateway. Centralized management. 

This is done through a distributed AWS Network Firewall deployment model using AWS Firewall Manager. For centralized, through a single instance of AWS Network Firewall and then a combination through AWS firewall Manager. Now, what about source IP visibility? Well, for distributed and a combined AWS deployment model, configuration dependent, but with centralized, yes, supported. What about the potential of a misconfiguration or a blast radius? With distributed, it's the lowest. With centralized, it has a medium risk, and a combination, it is low. What about cost? For distributed, per AWS Firewall Endpoint, for centralized, per AWS Transit Gateway attachments and AWS Network Firewall Endpoints plus AWS Transit Gateway data processing. 

That also goes for the combined AWS Network Firewall deployment model. Some considerations when utilizing any of the deployment models we just talked about. AWS Network Firewall is a managed service by AWS and is highly available based on AWS Hyperplane technology. Multiple instances are scaled to support the traffic flow. Also take note, AWS Transit Gateway is required for centralized and a combined deployment model. And the last one, AWS Network Firewall endpoints are utilized, so you need to consider the cost per endpoint and only deploy them where it's required.