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# EIP & ENI

### **EIP**

**Introduction**

* A static IPv4 address on AWS. Can attach to / detach from EC2 / NAT / ELB

**Scenario**

* Migrate on-premises instances with static trusted IP addresses to AWS
  * Bring the address range to AWS, it appears in your account as an address pool.
  * Create Elastic IP addresses from your Bring Your Own IP (BYOIP) address prefix and use them with AWS resources such as EC2 instances, Network Load Balancers, and NAT Gateways.

### [**ENI**](https://docs.aws.amazon.com/AWSEC2/latest/UserGuide/using-eni.html)

**Introduction**

* A virtual network card in VPC

**Scenario**

* Can assign multiple IPs to an EC2 instance for
  * Host multiple websites by using multiple SSL certificates. Associating each certificate with a specific IP address.
  * Operate network appliances, such as firewalls or load balancers, that have multiple IP addresses for each network interface.
  * Redirect internal traffic to a standby instance in case your instance fails, by reassigning the secondary IP address to the standby instance.


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