Using VPC Flow Logs to de-risk network migration

Network administrators rely heavily on VPC Flow Logs for visibility into their network traffic. Last year, we updated VPC Flow Logs to offer expanded network traffic visibility, extending beyond subnets to include VLAN attachments and VPN tunnels. This enhancement provides comprehensive monitoring of network traffic across your on-premises and multi-cloud environments.

Now, with VPC Flow Logs for VLAN attachments, you can export detailed telemetry data for your network traffic traversing Cloud Interconnect. This data encompasses essential information such as source and destination IP addresses, ports, protocols, bytes/packets transferred, timestamps, and other relevant metadata. These logs are crucial for a variety of use-cases, including network traffic analysis, troubleshooting, capacity planning, and maintaining compliance and security. Then, you can use Flow Analyzer to quickly analyze your VPC Flow Logs to gain valuable insights into your network without writing complex SQL queries. 

Sounds great, but how do you use it? Hackensack Meridian Health (HMH) is a leading not-for-profit healthcare organization and the largest hospital system in New Jersey. As a network of hospitals, urgent care centers, and physician practices, system reliability is extremely important and a cornerstone value of HMH. In this blog post, we demonstrate how HMH leveraged VPC Flow Logs and Flow Analyzer to analyze their Cloud Interconnect traffic prior to migrating their Google Cloud network to a new architecture design.

Let’s jump in.

Using VPC Flow Logs to prepare for migration

Last year, HMH was getting ready to migrate their critical, large-scale network to a newer Google Cloud network design. Before a migration of this scale, they wanted to use sankey diagrams to get a clear understanding of their most important hybrid traffic patterns. This analysis was the only way to accurately identify — and proactively plan for — the biggest risks that could cause disruption during the cutover.

“Getting a clear picture of our interconnect traffic always felt like a black box. Enabling VPC Flow Logs and feeding it into Flow Analyzer finally gave us the ‘who-is-talking-to-what’ map we needed. Identifying those critical traffic flows before we changed any routes was key to de-risking the entire migration.” – Randall Brokaw, Cloud Engineering Manager, Hackensack Meridian Health

To collect the necessary data, HMH enabled VPC Flow Logs on all of their VLAN attachments, then leveraged Flow Analyzer to easily aggregate the ingress and egress data. The following query components were used for ingress analysis: