A company is deploying a new web application that uses a three-tier model with a public-facing Network Load Balancer and web servers in an Amazon VPC. The application servers are hosted in the company’s data center. There is an AWS Direct Connect connection between the VPC and the company’s data center. Load testing results indicate that up to 100 servers, equally distributed across multiple Availability Zones, are required to handle peak loads.
The Network Engineer needs to design a VPC that has a /24 CIDR assigned to it.
How should the Engineer allocate subnets across three Availability Zones for each tier?
A. Network Load Balancer: /29 per subnetWeb: /26 per subnet
B. Network Load Balancer: /28 per subnetWeb: /25 per subnet
C. Network Load Balancer: /28 per subnetWeb: /27 per subnet
D. Network Load Balancer: /28 per subnetWeb: /26 per subnet
A is Correct.
A & D are the only viable correct answers because they correctly provide for /26, which is BS 64, you then have the following subnets, 0 / 64 / 128 and 192 each giving you 64 IP Addresses. Take away the unusable and reserved IP Addresses, you’re left with roughly 60 usable addresses multiplied by 3 AZs this is more than adequate for 100 devices across the /24 VPC.
/29 for the ALB gives you 32 subnets each with 6 usable IP addresses (only the top primary subnet reserves GW, DNS, and 3rd IP, etc) so you have 6 usable ip addresses and you only need 1 for the NLB per AZ.
D