Learn which AWS services support CIDR block notation for defining IP address ranges. Understand how Security Groups and Network ACLs use CIDR in AWS to manage network security effectively.
Table of Contents
Question
Which of the following AWS services or features allow CIDR block notation when providing an IP address range? (Select TWO.)
A. Security groups
B. Amazon Machine Image (AMI)
C. Network access control list (network ACL)
D. AWS Budgets
E. Amazon Elastic Block Store (Amazon EBS)
Answer
A. Security groups
C. Network access control list (network ACL)
Explanation
The correct answers are A and C because security groups and network access control lists (network ACLs) are AWS services or features that allow CIDR block notation when providing an IP address range. Security groups act as a virtual firewall for the associated Amazon EC2 instances, controlling inbound and outbound traffic at the instance level. Network ACLs act as a firewall for the associated subnets, controlling inbound and outbound traffic at the subnet level. Both security groups and network ACLs use CIDR block notation to specify the IP address ranges that are allowed or denied.
Security Groups
Security Groups in AWS act as virtual firewalls for your EC2 instances, controlling inbound and outbound traffic. When configuring rules for a Security Group, you can specify IP address ranges using Classless Inter-Domain Routing (CIDR) notation. For example:
- 203.0.113.0/24 allows traffic from all IPs in the range 203.0.113.0 to 203.0.113.255.
- 0.0.0.0/0 allows traffic from all IPv4 addresses globally.
This flexibility enables precise control over which IP ranges can access your resources, making CIDR essential for scalable and secure network configurations.
Network Access Control List (Network ACL)
Network ACLs operate at the subnet level and provide an additional layer of security by allowing or denying traffic based on rules defined with CIDR blocks. For instance:
- A rule with 10.0.0.0/16 allows or denies traffic for all IPs in the range 10.0.x.x.
- IPv6 ranges can also be specified, such as 2001:db8::/64.
Network ACLs are stateless, meaning both inbound and outbound rules must be explicitly defined using CIDR notation to manage traffic effectively.
Why Not the Other Options?
B. Amazon Machine Image (AMI): AMIs are pre-configured templates for launching EC2 instances and do not involve specifying IP address ranges.
D. AWS Budgets: This service is used for cost management and does not deal with networking or IP configurations.
E. Amazon Elastic Block Store (EBS): EBS provides storage volumes for EC2 instances and does not involve network-related configurations like CIDR.
By focusing on Security Groups and Network ACLs, you can effectively manage network security using CIDR block notation in AWS environments.
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