Subnet Groups

5 minutes 5 Questions

Subnet Groups are collections of subnets that reside within an Amazon Virtual Private Cloud (VPC). They are used to simplify the process of deploying ElastiCache clusters within a VPC. Subnets within a group will be distributed among multiple Availability Zones (AZ) to ensure high availability and fault tolerance. When you create an ElastiCache cluster in a VPC, you can specify a Subnet Group, and the cluster will be automatically deployed across all the subnets within the subnet group. This enables you to control network access, meet security requirements, and ensure fault tolerance for your ElastiCache clusters by launching them within a VPC.

AWS Solution Architect: Understanding Amazon ElastiCache - Subnet Groups

What is Amazon ElastiCache Subnet Groups?

A subnet group is a collection of subnets that may be designated specifically for Amazon ElastiCache in a Virtual Private Cloud (VPC) within AWS. Each subnet group should contain one or more subnets from various Availability Zones (AZ) within the same region.

Why is Amazon ElastiCache Subnet Groups important?

High Availability: Spreading nodes across several subnets in various AZs significantly improves the High Availability of the data store. In case of problems with one AZ, the remaining nodes in other AZs are unaffected.
Security: By deploying ElastiCache in the VPC and using subnet groups, you can isolate your cache clusters and control access using VPC security group rules.
Scalability: Subnet groups enable the scalability of cache clusters.

How Amazon ElastiCache Subnet Groups work?

When you launch a node or cluster, you select the subnet group. Nodes are then distributed across the subnets of the subnet group.

Exam Tips: Answering Questions on Subnet Groups

1. Know the definition of subnet groups and their functionality.
2. Understand the benefits of using subnet groups, including high availability, heightened security, and scalability.
3. Recognise how to implement subnet groups by selecting them when launching nodes/clusters.

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Question 1

You are designing an application that requires three separate subnets in a VPC for a production environment. You need to ensure quick failover and provide low-latency among subnets. Which subnet group configuration would you recommend?

3 subnets in different Availability Zones within the same region 2 subnets in one Availability Zone, and 1 subnet in another Availability Zone within the same region 3 subnets spread across different regions 3 subnets in the same Availability Zone

Correct Answer: 3 subnets in different Availability Zones within the same region

In order to provide quick failover and low-latency connections between subnets, it is recommended to have each subnet in a different Availability Zone within the same region. This configuration provides redundancy and improved performance among the subnets.

Question 2

You are designing a highly sensitive application that needs to maintain a secure network environment. Which method should you use to create subnet groups to ensure the highest level of security?

Use default tenancy within a single VPC Use default tenancy with individual VPCs for each subnet group Use dedicated tenancy with individual VPCs for each subnet group Use dedicated tenancy within a single VPC

Correct Answer: Use dedicated tenancy with individual VPCs for each subnet group

Higher levels of security can be achieved by utilizing dedicated tenancy with individual VPCs for each subnet group. This ensures that each subnet group is completely isolated, ensuring no other tenants or users have access to your subnet groups.

Question 3

Your application includes a database that utilizes Amazon RDS. You are required to place the database in a subnet group for high availability. How should the subnet group be configured?

Create a subnet group with multiple subnets in different Availability Zones Create a subnet group with multiple subnets in the same Availability Zone Create a subnet group with multiple subnets in different regions Create a subnet group with only one subnet

Correct Answer: Create a subnet group with multiple subnets in different Availability Zones

RDS uses subnet groups for high availability by creating a primary database instance in one Availability Zone and a standby instance in another. This requires a subnet group with multiple subnets in different Availability Zones to allow for automatic failover in case of an outage.

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