With a Redshift cluster in AWS, you are trying to use SQL Client tools from an EC2 Instance. But you aren`t able to connect to the Redshift Cluster. What must you do to ensure that you can connect to the Redshift Cluster from the EC2 Instance?

Answer options:

A.Install Redshift client tools on the EC2 Instance first.
B.Modify the Security Groups.
C.Use the AWS CLI instead of the Redshift client tools.
D.Modify the Route Table of the subnet.

Correct Answer – B
AWS Documentation mentions the following.
By default, any cluster that you create is closed to everyone. IAM credentials only control access to the Amazon Redshift API-related resources: the Amazon Redshift console, Command Line Interface (CLI), API, and SDK. To enable access to the cluster from SQL client tools via JDBC or ODBC, you use security groups:
If you are using the EC2-Classic platform for your Amazon Redshift cluster, you must use Amazon Redshift security groups.
If you are using the EC2-VPC platform for your Amazon Redshift cluster, you must use VPC security groups. 
For more information on Amazon Redshift, please refer to the URL below.
http://docs.aws.amazon.com/redshift/latest/mgmt/overview.html