Firewalls are a critical component of your security architecture. With the increased migration of workloads to cloud environments, more companies are turning to cloud-first solutions for their network security needs. 

Google Cloud Firewall is a scalable, cloud-first service with advanced protection capabilities that helps enhance and simplify your network security posture. Google Cloud Firewall’s fully distributed architecture automatically applies pervasive policy coverage to workloads wherever they are deployed in Google Cloud. Stateful inspection enforcement of firewall policies occurs at each virtual machine (VM) instance. 

Cloud Firewall offers the following benefits: 

1. Built-in scalability: With Cloud Firewall, the firewall policy accompanies each workload as part of the forwarding fabric, which enables the service to scale intrinsically. This can relieve customers of the operational burden to spend time and resources to help ensure scalability. 

2. Availability: Cloud Firewall policies automatically apply to workloads wherever they are instantiated in the Google Cloud environment. The fully distributed architecture can allow for precise rule enforcement, even down to a single VM interface.  

3. Simplified management: Cloud Firewall security policies for each workload are independent of the network architecture, subnets and routing configuration. The context-aware and dynamically updating objects for firewall rules enable simplified configuration, deployment and ongoing maintenance.

How to migrate from on-prem to Cloud Firewall 

Most on-premises firewall appliances, either virtual or physical, are deployed in one of two modes: 

1. Zone-based that creates trusted and untrusted zones to apply firewall policies; or 

2. Access Control Lists (ACL) applied to an interface. 

In both cases, the firewall’s primary purpose is to protect one perimeter or network segment from another. For example, you may use a zone based firewall to filter traffic from an “untrusted” to a “trusted” zone. Similarly, you may have an ACL-based firewall to protect an “inside” network segment from an “outside” network segment.  

However, that strategy is not the best approach with Google Cloud Firewall policies and rules. Cloud Firewall is not designed to act as a perimeter device; rather, Cloud Firewall is a fully distributed set of rules to help protect individual resources, such as VMs. However, most of our customers want to replicate their on-prem firewall logic and apply it to their cloud environment.  Take the following example:

There are a lot of similar components shared between on-prem firewall appliance rules and Cloud Firewall rules. However, some critical differences between them can make a migration from firewall appliances to Cloud Firewalls a challenging task, for example:

• Traditional firewalls protect a perimeter. In Google Cloud, firewall rules protect resources. This is done through the concept of “targets,” which specify which resources a given firewall rule applies to.

• There are multiple types of firewall options available in Google Cloud (hierarchical firewall policies, global/regional firewall policies, and Virtual Private Cloud (VPC) firewall rules). Deciding which type of rules to use, and how to configure the rules with your cloud network architecture requires review and planning. 

Furthermore, there are some additional firewall rules that may be needed in a cloud environment when compared to an on-prem firewall. For example, you may need to create ingress firewall rules to allow Google Cloud health check traffic to load balancer backends or you may need to create an egress rule to allow VMs access to use the Google Cloud APIs. Further, on-prem firewalls often have additional functions in on-prem networks including routing, NATing, VPN termination, and in some cases, Layer 7 inspection.

To assist customers with the migration from on-prem firewall appliances to Cloud services, including Cloud Firewall, we have developed a best practice guide that includes design and architecture considerations, and a side-by-side comparison of on-prem to Cloud Firewall rules. Check out the guide here for more information.