Elastic IP addresses in AWS - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is an Elastic IP address in AWS?

An Elastic IP address is a static, public IPv4 address designed for dynamic cloud computing. It lets you mask instance or availability zone failures by quickly remapping the address to another instance.

beginner

Why should you avoid leaving Elastic IP addresses unattached to running instances?

AWS charges for Elastic IP addresses that are allocated but not attached to a running instance to encourage efficient use of public IPs.

intermediate

How do Elastic IP addresses help with instance failure recovery?

You can quickly remap an Elastic IP address from a failed instance to a healthy one, minimizing downtime and maintaining the same public IP for clients.

intermediate

Can you associate multiple Elastic IP addresses with a single EC2 instance?

Yes, you can associate multiple Elastic IP addresses with a single instance if it has multiple network interfaces or secondary private IP addresses.

beginner

What is the difference between a public IP and an Elastic IP in AWS?

A public IP is assigned dynamically and changes when an instance stops or starts. An Elastic IP is static and remains the same until you release it, allowing consistent addressing.

What happens if you allocate an Elastic IP but do not associate it with a running instance?

A The Elastic IP is free to keep indefinitely

B The Elastic IP is automatically released

C The Elastic IP is assigned to a random instance

D You will be charged for the unused Elastic IP

AWS charges for Elastic IP addresses that are allocated but not attached to a running instance to encourage efficient use.

Which of the following best describes an Elastic IP address?

A An IPv6 address assigned to an instance

B A private IP address within a VPC

C A static public IPv4 address you can move between instances

D A dynamic IP address assigned at instance launch

Elastic IP addresses are static public IPv4 addresses that you can remap between instances.

How can Elastic IP addresses improve fault tolerance?

A By allowing quick remapping to a healthy instance after failure

B By automatically backing up instance data

C By increasing instance CPU capacity

D By encrypting network traffic

Elastic IPs let you quickly remap the address to another instance to reduce downtime.

Can you have more than one Elastic IP address associated with a single EC2 instance?

A Yes, if the instance has multiple network interfaces or secondary private IPs

B No, only one Elastic IP per instance is allowed

C Yes, but only in different regions

D No, Elastic IPs are shared across instances

Instances with multiple network interfaces or secondary private IPs can have multiple Elastic IPs.

What is the main difference between a public IP and an Elastic IP in AWS?

A Public IPs are static; Elastic IPs are dynamic

B Public IPs change on stop/start; Elastic IPs remain static until released

C Public IPs are only for private networks; Elastic IPs are public

D There is no difference

Public IPs assigned at launch can change when the instance stops and starts, while Elastic IPs remain fixed.

Explain what an Elastic IP address is and why it is useful in AWS.

Think about how you keep the same phone number even if you change phones.

Describe the cost implications of Elastic IP addresses and how to avoid unnecessary charges.

Unused resources in the cloud often cost money.