I have an EC2 Instance with a Public IP associated.
For no reason, after a restart, this association is lost and I have to reassociate.
It doesn't happen for every restart.
Any tips?
There are two types of public IP addresses available for Amazon EC2 instances:
A Public IP address that is randomly assigned to an instance from a pool of available addresses. If an instance is stopped and later started, it might receive a different public IP address. (Restarting an instance will not cause this to happen, so I suspect that you stopped your instance rather than merely restarted it.)
An Elastic IP address that can be allocated to your account. The address can then be allocated to an EC2 instance. The IP address is static, so it will not change. However, it can be reassigned to a different EC2 instance if desired. It remains associated with the account until it is released.
If you are saying that you were using an Elastic IP address, then it should remain associated with the instance until specifically dissociated. It will not dissociate without a specific request. If it is being dissociated, then you could use AWS CloudTrail to look for the API call that would have caused this to happen.
In AWS EC2, By default the EC2 instances are not assigned with static public IP address.
For that, you will have to generate a Static IP address first and then assign it to your EC2 instance. In this way, even after the restart, it will retain the allocated static IP address.
To do this, Navigate to EC2 service, select 'Elastic IPs' from the left menu. Click on Allocate Elastic IP address. This will generate the static IP address. Now to allocate this to your instance, select the checkbox against the newly generated IP address, and click on Actions and 'Associate Elastic IP address'
Hope this helps :)
Related
I have an instance inside a VPC with DNS hostnames & DNS resolution enabled
Today, each instances I spawn get the hostname & Private IP DNS name as
ip-xx-xx-xx-xx.ec2.internal
The problem with this is everytime my instance is terminated and I have to replace it, the IP address is going to change. Other machines in the same VPC need a deterministic way to access this instance. e.g. by connecting to mymasterinstance.dev. Any idea how do I give an internal / private DNS for my instance?
Private IP addresses on Amazon EC2 instances do not change. Therefore, the other machines could simply reference the private IP address.
Alternatively, you can create a "Private hosted zone" in Amazon Route 53 and create an A-Record to associate a domain name (eg mymasterinstance.dev) with the private IP address of the instance.
The public IP address on an instance will change when the instance is Stopped and Started (but will not change when the instance is Rebooted). If you require a static public IP address, you can create an Elastic IP Address and associate it with the instance.
Another perhaps simpler way to do this is to add a second IP address to your EC2 instance. When you terminate an instance, and add back a "replacement" instance, set its second IP address to what the terminated instance's second IP address was. Then you can do all of your referencing directly by IP address and you have full control over that second IP address. None of your configs needs to change.
Our team has isolated instance of EC2 that's shutdown overnight to save resources. When it starts up, it has different IP address and they can't access it from internal network as its IP address has changed and need to be added to the WAF.
Is there a process via SNS, Lambda or something that I can run after launch that automates it?
The easiest method is to create an Elastic IP addresses, which is a static public IP address. Then, allocate that Elastic IP address to the Amazon EC2 instance.
The Elastic IP address will remain the same even when the instance is stopped and started.
I launch AWS EC2 instances with a userData field that runs the desired initialization jobs. One of the initialization commands is to run an infinite time background process. My question is that since AWS EC2 instances change IP addresses frequently, will my infinite time background process be killed upon a change in that instance's IP? I am not changing the instance's state after I launch it. When I initialize my instances, the jobs are working fine, I just don't know whether that behavior will continue upon an IP change since I don't have a way for rigorously testing this.
The SSH connection termination might be due to your ISP having changed your own public IP address, or a similar networking issue on your or your provider's side, and not the EC2 instance having changed. An EC2's IP address only changes under certain well-defined circumstances that I'll describe below:
An EC2 instance's private IP address: Once an EC2 instance is launched, it's assigned a private IP address at boot time. An instance's private IP address will never change during the lifetime of that instance.
An EC2 instance's public IP address: When an instance is launched, you control whether it receives a public IP or not. The public IP address never changes automatically, but can change under the circumstances described below.
AWS releases your instance's public IP address when it is stopped, hibernated, or terminated. Your stopped or hibernated instance receives a new public IP address when it is started.
AWS releases your instance's public IP address when you associate an Elastic IP address with it. When you disassociate the Elastic IP address from your instance, it receives a new public IP address.
To answer your original question: You don't need to worry about an EC2 instance regularly changing its IP address because as long as it keeps running and you don't explicitly change the associated IP address yourself, the IP address will remain static.
If you want to retain a public IP address that persists even after hibernating, stopping, or terminating the instance, you can attach an Elastic IP address.
For more information see: What are Elastic IP addresses, and how do I use them?
I am new to AWS and tried to create an EC2 instance.
I have a domain and ready to modify the A record to the associated EC2 instance.
I found an article that said an elastic IP is required for associating a production domain.
But AWS provides a public IP and it is accessible on the public internet too (i know it changes after restart, just assuming its okay to modify the A record after the machine is restarted - actually it is not restart very often).
In this case, is it a must that to assign an elastic IP to the instance (this instance contains no load balancing, it is only a simple single instance)?
If yes, why is it necessary?
An Elastic IP (EIP) is not necessary provided that you understand the limitations of public IPs. You may not reboot your instance, but AWS might for any number of reasons. This means that the public IP address could change when you are not expecting it.
When an EIP is assigned to a running EC2 instance, there are no charges for the EIP e.g. it is free. Therefore why go thru the hassle of needing to monitor your public IP address.
Given an address (not owned by me) which is part of Amazon's Cloud, is there any way I can tell if that address is "elastic" (static)?
There is no way to tell if an IP is static(elastic) or not. AWS publishes a list of CIDRs that it owns and updates it periodically, but no information on if the addresses are elastic or not.
If the address is owned by you, then you can call describe-addresses and check if the IP is in the output. But if you don't own it, there is no way to tell if the address is elastic or not.
AWS provides you the flexibility to get Elastic Ip addresses in 2 ways
if generated with Elastic Ip console, yes it is static and completely owned by you, unless you delete it or re-associate it.
If you are referencing to Auto Assigned Elastic Ip address with EC2/ELB, they are not static. you get a new ip address everytime you restart the instance/add or remove the instance from ELB.
Elastic Ip addresses are associated to instances, which already have an IP address(static until instance terminated)