I have 2 instances running and a web application in one of them (Say instance1) uses private IP of another instance (Say instance2) to call a service.
I restarted instance2(IP changes after restart) and restarted the web application on instance1 after adjusting the configurations accordingly, and application was up and running successfully.
But then suddenly it stopped responding after 2 hours and when I looked for the problem, I found that the private IP of the instance2 was again changed while it was running.
Has it happened with anyone else? If yes what's the solution for this?
The private IP address of an Amazon EC2 instance will never change.
It will not change while an instance is running.
It will not change while an instance is stopped.
You cannot change a private IP address. (However, I think that if you assign multiple private IP addresses, you can add/remove the secondary addresses, but not the primary IP address.)
You cannot launch another instance with the same private IP address of another instance (in the same VPC), even if the other instance is stopped.
The above only applies to the private IP address, not the public IP address.
In you case you need to keep your public address from changing after instance shutdown. Take a look on using ElasticIP Using ElasiticIP with EC2 instances
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I have create an AWS EC2 instance and, I have stopped the instance for some reasons. When I start the instance back, I happen to notice that the public IP address have changed but, the private IP address remains unchanged.
I assume that the public IPs address will be released from the instance and move to the public IP pool since it is dynamic IP address unless we attach an Elastic IP address.
May I ask why the private IP address remains unchanged and what is the reason/purpose behind that?
I have tried googling but couldn't find the exact answer. I appreciate your input and help on this.
It's just a function of how AWS VPCs work. From the documentation:
A private IP address remains associated with the network interface when the instance is stopped and restarted, and is released when the instance is terminated.
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.
I recently moved a small R project from a regular EC2 instance to an instance behind a VPC. I installed rstudio-server as normal, and it seems to be running. However, unlike a regular EC2 instance, there is no public DNS to connect to. (There is a public IP address, but going there doesn't seem to do the trick.)
In this case, what browser address should I go to to access rstudio server?
Many thanks!
You have launched the instance in VPC. Here is the check list:
When launching the instances in VPC, make sure you launch it in the public subnet of your VPC. Else it will not be accessible from outside
When launching the instances in VPC (presuming public Subnet), do ensure that you check a box which says something like "assign a public IP address to the instance" at the time of creating the instance. By default this is not checked. So if you fail to check this box, then Instance will not have a public host name. You can however, assign an elastic IP later on.
Make sure you VPC security groups are configured properly to allow necessary incoming/outgoing access. In your case, incoming access on port 80 is/443 is essential.
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 :)