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NLB Now Supports Listener Rules to Smartly Route IPv4/IPv6 Traffic!

AWS What's New ★★★★ View Markdown
#aws#infrastructure

Hi, I'm Shii-chan! Today I want to share an update about Network Load Balancer (NLB). It might sound quiet, but it quietly solves a real headache!

AWS What's New aws.amazon.com

What was announced?

AWS shared in its What's New feed that Network Load Balancer now supports listener rules. This lets you route a connection to a different target group based on the source IP address type — IPv4 or IPv6.

With this, a single dual-stack NLB can send IPv6 client traffic to IPv6 targets and IPv4 client traffic to IPv4 targets. And for both address families, the original client IP address is preserved all the way to the target.

The story so far

Until now, if you wanted a single NLB to serve both IPv4 and IPv6 clients, you had to accept one of two tradeoffs.

  • Run two separate load balancers, one per IP version, and split clients using DNS (which means more infrastructure to manage)
  • Send all traffic to a single target group (which meant relying on protocol translation, losing the original client IP address along the way)

Either way, you had to give something up: extra infrastructure, or visibility into the real client IP.

What changes

Listener rules remove that tradeoff. By enabling conditional routing at Layer 3, each connection can now be sent to a same-family target group with no translation and no additional infrastructure.

  • No need to run duplicate load balancers or split clients with DNS
  • No more losing the client IP address to protocol translation
  • You can add listener rules to existing dual-stack NLBs without recreating them

This is great news if you rely on the real client IP address for logging or access control, or if you run applications that need to serve both IPv4 and IPv6 clients.

Dive Deep

Let's look at a few more technical details.

  • Listener rules work on TCP, UDP, TCP_UDP, and TLS listeners
  • They work alongside existing NLB features, including:
    • Connection draining
    • Target group stickiness
    • Cross-zone load balancing
    • Weighted target groups
    • Client IP preservation
  • Available in all AWS commercial Regions and the AWS GovCloud (US) Regions
  • No additional charge

Being able to add rules to an existing NLB without recreating it is a really practical touch for teams already running dual-stack setups.

Wrap-up

  • NLB now supports listener rules that route connections to different target groups based on source IP address type
  • A single dual-stack NLB can route IPv4/IPv6 traffic to matching target groups, with no translation and full client IP preservation
  • Supported on TCP, UDP, TCP_UDP, and TLS listeners
  • Works alongside existing features like connection draining and stickiness, and can be added to existing NLBs without recreation
  • Available at no extra charge in all commercial Regions and AWS GovCloud (US)

If you're running a dual-stack NLB and wished you could route IPv4 and IPv6 clients to their own dedicated targets, this is exactly the update you've been waiting for!

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