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Kiran
Kiran

Reputation: 539

AWS: Internet facing and Internal ALBs

I accidentally attached same instance with two target groups, of which one is selected for Internet facing and another is for Internal ALB. I had two different paths set for health checks for corresponding ALBs.

Even though subnets selected while creating ALBs are different(different subnet for Zone), how both ALBs are hitting corresponding healthcheck paths in the only instance running on subnet configured for internetfacing traffic??

I assumed ALBs should hit instances which are running in configured subnets, not hit instances running in other Subnets.

What is the intended behavior for this setup?

BRs, Kiran

Upvotes: 2

Views: 2033

Answers (1)

John Rotenstein
John Rotenstein

Reputation: 269951

By default, all subnets can communicate with each other. So, a Load Balancer in Subnet A can still perform health checks against instances in Subnet B.

The 'configured subnets' specify where the Load Balancer interfaces with the VPC (shown as Elastic Network Interfaces, ENIs). From that entry point, they can communicate with the other subnets.

Upvotes: 2

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