Elastic IP addresses (EIPs) are static, public IPv4 addresses designed for dynamic cloud computing within AWS. Unlike standard public IP addresses that change when an instance stops and starts, Elastic IPs remain constant, providing a persistent endpoint for your applications.
Key characteristics …Elastic IP addresses (EIPs) are static, public IPv4 addresses designed for dynamic cloud computing within AWS. Unlike standard public IP addresses that change when an instance stops and starts, Elastic IPs remain constant, providing a persistent endpoint for your applications.
Key characteristics of Elastic IP addresses include:
**Allocation and Association**: You first allocate an EIP to your AWS account, then associate it with an EC2 instance or network interface. This two-step process allows flexibility in managing your public IP addresses across resources.
**Regional Scope**: EIPs are region-specific resources. An EIP allocated in us-east-1 cannot be used in eu-west-1. However, you can move EIPs between Availability Zones within the same region.
**Pricing Considerations**: AWS charges for EIPs when they are not associated with a running instance or when multiple EIPs are associated with a single instance. This encourages efficient resource utilization and prevents IP address hoarding.
**Use Cases**: EIPs are valuable for scenarios requiring consistent IP addresses, such as DNS configurations, whitelisting for firewalls, or failover architectures where you need to quickly remap addresses to standby instances.
**Automation and Provisioning**: Using AWS CloudFormation or the AWS CLI, you can automate EIP allocation and association. CloudFormation templates can define EIPs as resources and establish dependencies with EC2 instances for streamlined deployments.
**Limits**: By default, each AWS account has a limit of 5 EIPs per region, though this can be increased through a service limit request.
**Best Practices**: Consider using Elastic Load Balancers or Route 53 for high availability instead of relying solely on EIPs. For IPv6, AWS provides persistent addresses by default, eliminating the need for an equivalent EIP concept.
Understanding EIP management is essential for SysOps Administrators when designing resilient, automated infrastructure deployments.
Elastic IP Addresses - Complete Guide for AWS SysOps Administrator Associate
What is an Elastic IP Address?
An Elastic IP (EIP) address is a static, public IPv4 address designed for dynamic cloud computing. Unlike regular public IP addresses that change when you stop and start an EC2 instance, an Elastic IP address remains constant and can be quickly remapped to another instance in your account.
Why are Elastic IP Addresses Important?
Elastic IP addresses are crucial for several reasons:
• High Availability: You can mask the failure of an instance by rapidly remapping the address to another instance • Static Addressing: Essential for applications that require a fixed IP address, such as DNS configurations, firewall rules, or third-party integrations • Disaster Recovery: Enables quick failover by reassigning the IP to a standby instance • External Communication: Provides a consistent endpoint for external systems to reach your applications
How Elastic IP Addresses Work
1. Allocation: You allocate an Elastic IP address from Amazon's pool of public IPv4 addresses or bring your own IP addresses (BYOIP)
2. Association: Once allocated, you associate the EIP with an EC2 instance or a network interface
3. Remapping: You can disassociate an EIP from one instance and associate it with another instance, typically completing within a few minutes
4. Release: When you no longer need the EIP, you release it back to the pool
Key Characteristics:
• EIPs are regional - they can only be used within the region where they were allocated • An EIP can be associated with only one instance or network interface at a time • When you associate an EIP with an instance that already has a public IP, the original public IP is released • EIPs work with both EC2-Classic (deprecated) and VPC environments
Pricing Considerations
• No charge: When an EIP is associated with a running instance • Charged: When an EIP is allocated but not associated with a running instance • Charged: When associated with a stopped instance • Charged: For additional EIPs associated with an instance (you get one free per running instance) • Data transfer charges apply for data transferred through EIPs
Limits and Quotas
• Default limit: 5 Elastic IP addresses per region per AWS account • This limit can be increased by requesting a quota increase through AWS Support • Each VPC can have multiple EIPs up to your account limit
Common Use Cases
• Hosting websites that require a static IP for DNS A records • Running mail servers that need consistent IP addresses • Implementing failover solutions for critical applications • Whitelisting IP addresses in partner or client firewalls • Running applications that require IP-based licensing
Exam Tips: Answering Questions on Elastic IP Addresses
Tip 1 - Understand Billing Scenarios: Questions often test whether you know when EIPs incur charges. Remember: you are charged when an EIP is not associated with a running instance. This includes stopped instances and unassociated EIPs.
Tip 2 - Know the Default Limits: The default limit is 5 EIPs per region. If a scenario mentions needing more, think about requesting a quota increase.
Tip 3 - Regional Scope: EIPs are regional resources. They cannot be transferred across regions. For multi-region architectures, you need separate EIPs in each region.
Tip 4 - Failover Scenarios: When questions describe high availability or failover requirements, EIPs are often part of the solution. They can be remapped quickly to healthy instances.
Tip 5 - VPC vs EC2-Classic: In VPC environments, EIPs can be associated with instances or network interfaces. This provides flexibility for network designs.
Tip 6 - NAT Gateway Association: EIPs are required for NAT Gateways. Each NAT Gateway needs exactly one EIP associated with it.
Tip 7 - Think Cost Optimization: If a question mentions reducing costs, releasing unused EIPs is often a valid answer. AWS charges for idle EIPs to encourage efficient resource utilization.
Tip 8 - Network Interface Association: EIPs can be associated with Elastic Network Interfaces (ENIs), not just instances. This enables more flexible networking patterns and is useful for moving addresses between instances by moving the ENI.
Tip 9 - Public IP Behavior: When you associate an EIP with an instance that has an auto-assigned public IP, the auto-assigned IP is released. This is a common exam topic.
Tip 10 - DNS Resolution: EIPs have associated public DNS hostnames. When an EIP is moved, DNS propagation may cause brief connectivity issues for clients using the DNS name rather than the IP address.