Network Load Balancer (NLB) Cross AZ Data Charges

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If I have a NLB (with cross region enabled) sending data to targets in 3 different AZ's but these AZ's are all in the same region and also everything is in the same VPC will there be any data transfer charges? I understand there will be other NLB charges - it is specifically the data transfer charges I need to confirm for this scenario.

There seems to different views on this. Also the AWS Documentation pages for NLBs (https://aws.amazon.com/elasticloadbalancing/) directs to Amazon EC2 pricing page for Data Transfer charges but that pages refers back to the ELB documentation. So if anyone can point me at the AWS documentation that covers this specifically that would also be much appreciated.

rmd
asked a month ago123 views
2 Answers
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Hello,

Yes there will be charges for traffic incoming on the NLB from az1 to az2 or az3 for instance. I came across this documentation, does it helps: https://docs.aws.amazon.com/elasticloadbalancing/latest/network/target-group-cross-zone.html

also a little more explanation about data transfer costs: https://aws.amazon.com/blogs/architecture/overview-of-data-transfer-costs-for-common-architectures/

Leoc2
answered a month ago
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EXPERT
reviewed a month ago
  • Thank you. This presentation from re:INVENT ( the slide entitled "What about Load Balancers") seemed to show that at least for ALB's there would be no charge if everything was in same VPC. https://d1.awsstatic.com/events/reinvent/2021/Demystify_data_transfer_charges_on_AWS_NET203.pdf

    The diagram on the left of that slide is for an ALB and shows no charges for cross AZ transfers (with Cross AZ enables on the ALB). The diagram to the right of the slide is for a NLB but does show a charge when crossing AZ's. So ALB's and NLB's must be treated different for crossing AZ's i guess.

    Am i right in thinking its actually 2 charges for both out and in ? ie Charge will AZ OUT (Data vol x $0.01) + AZ IN (Data vol * $0.01) ....so effectively Data vol * $0.02 ?

  • Thank you for sharing this link, it's very well done.

    Yes I understand it like you but with different use cases, like: Client connect from Az1 to NLB in Az2 then to target in Az1: it's going to be Data vol* 0.04$ Client connect from Az1 to NLB in Az1 then to target in Az2: Data vol * 0.02$

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For ALB and CLB, there is no cross-AZ data transfer charges within the same VPC. But for NLB, if the client and target are in one AZ, but the NLB is in another AZ, there will be a zone-in and zone-out which is $0.02.

profile pictureAWS
EXPERT
answered a month ago
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EXPERT
reviewed a month ago
  • Thank you. And if the client and NLB are in one AZ and the target is in another then I assume the same is also true ? ie zone in and out at $0.02 ?

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