3 BGP Route Policy Use Cases That Rule the Swamp

When Google Cloud launched BGP route policies for Cloud Router over a year ago, they gave network admins deep, programmable control over network paths. Now, with the new policy named sets, managing complex routing is even easier. Let’s dive into the top three use cases that have the capybaras buzzing.

1. Route Filtering: The Foundation of a Secure Swamp

Before you can steer traffic, you need to keep the bad routes out. Customers use BGP route policies to filter unwanted prefixes and prevent route leaks. By default, Cloud Router operates on a “fail open” model, but savvy engineers create a “fail closed” environment with a final “drop all” policy. This ensures absolute control and prevents BGP hijacking or blackholes.

• Dive deeper: Check out the Introduction to BGP policies for CEL expression basics.

2. Influencing Traffic Paths for Active/Standby Setups

Need to force traffic down a specific path for cost or redundancy? BGP route policies let you tweak MED and AS-PATH prepending without touching on-prem hardware. Make a peer preferred for incoming traffic by lowering MED, or deprioritize a backup link by prepending AS numbers. It’s like telling the caimans which channel to swim.

• Dive deeper: See the config steps in Using BGP policies to influence traffic paths.

3. Solving Asymmetric Routing with BGP Communities

Stateful firewalls require return traffic to flow back through the same appliance. Customers use BGP communities to tag routes on-premises, then Cloud Router reads those tags and adjusts MED to ensure symmetric routing. It’s a clever way to make Google Cloud respect your on-prem topology.

• Dive deeper: Learn how in Using BGP communities to create traffic symmetry.

Get Started Today

Take control of your dynamic routing with BGP route policies. Test your CEL expressions in staging first, then roll out to production. For full docs, see the BGP route policies overview.

Original announcement published on Google Cloud.