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.
Related
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 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
I have several instances on a vpc that communicate with each other through their private ips. Each instance was launched sometime ago and assigned a random public IP which is not used for anything. Since anything that is public presents a vulnerability and they are not used at all, I would like to removed them.
Is it possible to Remove public Ip Addresses without terminating the instance?
Yes you can remove a public IP address from an instance.
This solution applies when your instance was launched in a subnet with the "auto-assign public IP" setting enabled.
This makes AWS add a public IP address that seems hard to remove.
Notes:
If you change the subnet auto-assign setting and stop and start the instance,
this does not work, it has no effect. The public IP remains.
If you got your public IP by associating an elastic IP then it's
a different case and easy to fix; all you need to do is right-click on
the instance or on the Elastic IP, and choose "Networking", "Disassociate
Elastic IP Address")
There is a voted-down solution here that seems to work at first, but the public IP comes back (as a different address) when you start the instance up again.
Solution: (detailed steps below)
You need to first add another Network Interface, (so there are two or more N.Is), then you can release the public address by adding and removing an
elastic IP.
Here is a detailed step-by-step guide:
Create a new network interface.
Attach the new network interface to your instance. Now there will be two
or more network interfaces attached to your instance. This is important.
There MUST be two or more for this to work.
Create a new Elastic IP (in the EC2 console).
Right-click on the new EIP and associate it to the instance whose public IP
you want to remove. The original public IP will be replaced by the new one.
Now do the reverse of step 4, disassociate the EIP you have just added.
At this point, right-click on the instance and select "Networking", "Manage
IP addresses", you will see there are no public IPs on you instance any
more. at this point. You must refresh the instances view otherwise you
will not see this.
The public IP is now gone for good.
Even if you stop and start the instance, it will not return.
Tidy up: delete the elastic IP you created earlier. Don't delete the new
extra Network Interface. This has to stay in place. If you remove the new /
second NI then the public IP will come back the next time you stop and
start the instance.
I know this sounds a bit strange, but it is in the AWS docs here and I've tested it and it works.
The relevant part from the AWS documentation on that page, is this: "If the public IP address of your instance in a VPC has been released, it will not receive a new one if there is more than one network interface attached to your instance."
Nope that is not possible without terminating the instance. If it was Elastic Ip then it would have worked.
The only option is Take AMI of the instance, terminate the instance and launch the AMI in the VPC without enabling Public Ip address for that instance.
Once you terminate the instance with that private IP you can assign that private ip again to a new Instance you created from the Image. (As long as it's in the same VPC and subnet) This way you don't need to update the private IPs off all the "instances on a vpc that communicate with each other through their private ips"
Steps worked for me:
Disable auto assign public IP setting on vpc subnet.
Stop the ec2 instance.
Open Network Interface Manage IP address settings and assign a secondary private IP.
Open Elastic IPs and associate an elastic IP to the ec2 with secondary private IP.
Start the Ec2 Instace.
Open Network Interface Manage IP address settings and unassign the secondary IP.
Done, now you can release the previously associated elastic IP.
Below worked
create temp-priv-ni same subnet private interface use default security group
eni-xx-temp-priv-ni
allocate new public elastic ip
associate new public elastic ip to instance
attach eni-xx-temp-priv-ni to same instance
check instance has two private ips and new public elastic ip and past public eip is gone
then
disassociate public eip
go to instance network interfaces and detach eni-xx-temp-priv-ni
server will be now with same private ip and its public ip gone
the new public ip and new private ips can be deleted
It is a very old thread but the easiest way of removing a public ip associated via VPC settings is:
create an elastic IP
assign the elastic ip to the host owning
the public ip that you want to release (the ip is released at this
step)
disassociate the ip address from the elasic ip management
screen.
I tried changing the location to Asia/Pacific(Sydney) and created an instance with default configuration and my instance is assigned to a US-based IP address.
I created another VPC with subnet using AWS IP range with Sydney-based list and then created an instance, my private IP is assigned to Sydney-based IP address but still my public IP address is assigned to some US-based IP address.
Is there any way I can get a Sydney-based IP address to my instance?
Have you tried creating an EIP in the Sydney region and attaching it to the instance then checking again? No guarantee that'll work, but your chances will certainly be better than getting a randomly assigned one.
How did you determine the IP was US based? I imagine that sometimes the IP blocks move around from region to region as demand shifts.. It might be possible to get an EIP stuck in the Sydney region. You could also probably script something out to do the following:
Create an EIP
Geo-locate it
2a. If it's not Sydney/Australia, destroy EIP ==> return to step 1
If the geo-locate resolves to Sydney/Aus, stop the script.
Good luck :)
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 :)