Got a quick question which might be totally silly but it's early in the morning. So I have a standard AWS VPC with an ELB, NAT instance and 2x EC2 instances for the application code. By the looks of the image bellow the internet gateway passes traffic the ELB and NAT instance. My question is why isn't the NAT instance in front or behind the ELB ? it looks like that the single bottleneck in this VPC could be the NAT instance if all traffic is going through there.
The NAT (Network Address Translation) server is used to provide outbound Internet connectivity for Amazon EC2 instances in a private subnet.
Incoming traffic will enter via the Load Balancers and any responses to this traffic will also exit via the Load Balancers. The Elastic Load Balancing service automatically scales based upon the amount of traffic (there is also a charge for traffic transferred).
If an EC2 instance in a private subnet wishes to initiate a connection to the Internet (eg to download updates, or to communicate with Amazon S3), it cannot send traffic "out" of the load balancers. Instead, the subnet would be configured to route traffic to the NAT server, which acts as a proxy for requesting data from the Internet.
It is possible that the NAT server could become a bottleneck. If so, modify the instance to use a larger Instance Type -- this not only adds CPU and RAM, but also network bandwidth.
In some cases, people might also use a NAT server for incoming traffic -- either as a jump-box for administrative purposes (to login to an instance in a private subnet) or to forward specific ports to a private server (via port forwarding). However, best practice would be to separate these functions to a different instance for security and management purposes.
Additional information: Since writing this answer, AWS has introduced a Managed NAT Gateway that can automatically scale. It is created in a single AZ, so you might want to run it in two AZs for High Availability.
I'm not sure how its working, if the loadbalacer is terminating over the APP Tier , then the instance launched in these subnet will have route-table configured with IGW not the NAT instance, which raises a question how to make outbound traffic on the public network which is configured over a loadbalalncer
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so currently in our infrastructure we are using ECS with an application load balancer for inbound traffic and a NAT gateway for outbound traffic. I am looking to configure both inbound and outbound traffic to have the same public IP address but I am not sure how this is done as I've tried may different ways to achieve this but nothing seemed to have worked. If we take a look at the below image our infrastructure is similar except that we us EC2 and not fargate as we prefer to maintain our own instances
Screen shot
I would be very thankful if anyone could please help me out with this
I don’t think this is possible. External traffic is always routed though a NAT gateway, and incoming either though unknown number of ever changing load balancers or directly to IP of the e.g. EC2 instance.
So I have just setup an application load balancer but I need a static IP to whitelist my database connection, I found Global Accelerator can do the job so I have set it up and assigned it to the ALB. All showing fine in the console but when I ping my domain (www.example.com), I don't see either of the 2 static IP's assigned... and when I whitelist both IP's my application still cannot connect.
Am I doing something wrong?
Edit: My database is Mongo DB hosted on the Atlas Cloud. In my staging environment I have secured the connection to a single server instance using that servers IP address. Now I'm moving to a production environment with a load balancer, I'm not quite sure how I would achieve the same result, since I have multiple EC2 instances which can be created/destroyed via autoscaling. My thinking is that I need to whitelist the load balancer IP address rather than individual instances.
I am assuming that your architecture is:
Domain name pointing to an Application Load Balancer in AWS
Load Balancer points to an Auto Scaling group of Amazon EC2 instances
The EC2 instances point to your MongoDB database hosted on the Atlas Cloud
You want an static IP address so that the database can permit access from the Amazon EC2 instances
While incoming traffic to the EC2 instances goes through the Load Balancer, please note that the connection from an EC2 instance to the database is a separate outbound connection that is established to the database. This traffic does not go through the Load Balancer. The only traffic coming 'out' of a Load Balancer is the response to requests that came 'in'.
The typical way to implement this architecture is:
Load Balancer in public subnets
Auto-Scaled Amazon EC2 instances in private subnets
A NAT Gateway in the public subnet(s)
This way, the instances in the private subnets can access the Internet via the NAT Gateway, yet they are fully isolated from traffic coming in from the Internet. It has the additional benefit that the NAT Gateway has a static IP address. All traffic going through the NAT Gateway to the Internet will 'appear' to be coming from this IP address.
For fault tolerance, it is recommended to put a NAT Gateway in at least two Availability Zones. Each will have its own static IP address.
Oh, and you could consider moving your database to Amazon DocumentDB (with MongoDB Compatibility), which would reduce latency between the application servers and the database.
I have a few elastic beanstalk applications on the same VPC (which can also be reduced to one application), and I'd like them to be accessible both via one IP address (both inbound and outbound traffic), and via their own URL. I've seen that this can be done via NAT, but I haven't found documentation on whether this is all traffic (in both directions) and if it can be done alongside the original endpoints. Another question is whether there is a better way to do this.
NAT is used to provide access to internet for instances in private subnets. In this case all instances in the subnet will have the same external IP. But you won't be able to access your private instances using that IP, it's only for outbound traffic.
In your case I'd go with a ELB. Following the best practices, keep your instances with running applications in private subnets and:
Have an external facing ELB in public subnets (you'll need at least 2 public subnets in different AZs).
Create a Target Group and add your instances with running apps to it.
Assign the Target Group to the listener on your ELB.
Configure the security groups on ELB and app instances to allow the traffic on the port the applications are serving (usually it's 8080).
As a result you'll have your instances accessible by the ELB URL. If you want to have a pretty URL, you can configure it in Route 53 and resolve it to the ELB URL.
Its not possible by using aws provided NAT cluster but can be achieved by hosting a box with both Load balancer and NAT running in the same instance with EIP, map your domain with that IP for incoming traffic, for outgoing traffic in the route table of private app subnet you configure the NAT as target for all the 0.0.0.0/0 route, But it is not the recommended approach since the front facing instance becomes SPOF.
The recommended way is using ELB as a front facing and NAT cluster as outgoing for high HA.
I need to design a cross-region cross-VPC architecture and i am not sure how i can restrict access to my resources
The requirement is that i need to run my web app in one region and my database in an another region.
Both the servers are inside private subnets. The web app has an auto scaling group and load balancer attached. The database server in the other region should only be accessible from this web app. I cannot use ip based restrictions as the IP of load balancer changes with time. What other option do i have?
The IP address of your Load Balancer is irrelevant because the Load Balancer is only used for incoming connections to your web server.
First, I should point out that having your database remote from your application is a poor architectural decision, which will slow down your application. Please reconsider it if possible!
You have not provided much information, so I will make the following assumptions:
VPC in Region A contains:
A Load Balancer in a public subnet
Web servers in a private subnet
VPC in Region B contains:
A database in a private subnet
In this situation, you wish to communicate between two private subnets in different VPCs that reside in different regions. For this, you could consider creating a private VPN connection via Amazon EC2 instances located in the public subnets of each VPC. This would use a software VPN such as OpenVPN or OpenSwan.
You should also consider how to achieve a High Availability option for this solution. A well-architected VPC would have your web servers deployed across multiple Availability Zones in Region A, with your database preferably in a multi-AZ configuration in Region B (assuming that you are using Amazon RDS). You should similarly design your VPN solution to be highly-available in case of failure.
An alternative is to put a NAT Server in the public subnet of the VPC in Region A and configure the private Route Table to send traffic through the NAT Server. This means that traffic going from the web servers to the Internet would all come from the public IP address associate with the NAT Server (not the Load Balancer).
However, the database is in a private subnet, so the traffic cannot be directly routed to the database so this is only half a solution. It would then either require the database to be in a public subnet (with a Security Group that only accepts connections from the NAT Server) or some type of proxy server in the public subnet that would forward traffic to the database. This would become way too complex compared to the Software VPN option.
We're setting up an Amazon VPC in which we will provision (for now) a single EC2 instance and one RDS instance. This is to 'extend our data center', and should only be using private subnet(s).
So actually, we have this setup, and it is working well (insert smiley face icon). For all intents and purposes, we're mirroring the VPC scenario 4 outlined by Amazon here: http://docs.aws.amazon.com/AmazonVPC/latest/UserGuide/VPC_Scenario4.html
tl;dr: A single VCP, with a VPN connecting to our corporate network. The VPN uses a Virtual Private Gateway (VPC end) and Customer Gateway (our end) to allow us access as necessary to the EC2, which contains a webserver connecting to the RDS instance as needed. Anyone on our network has access to the web server running on the EC2 via a URL. All this is working as expected.
The problem comes when the EC2 instance needs to access a resource on the Internet - The idea is for us to NOT have any public subnets, but to route all traffic from the EC2 instance through our VPN and out the 'standard' path of our corporate Internet access. However we're having trouble setting this up.
The fact that it can be done is hightlighted in Amazon's FAQ here:
https://aws.amazon.com/vpc/faqs/
Q. How do instances without public IP addresses access the Internet?
Instances without public IP addresses can access the Internet in one of two ways:
Instances without public IP addresses can route their traffic through a NAT gateway or a NAT instance to access the Internet. These instances use the public IP address of the NAT gateway or NAT instance to traverse the Internet. The NAT gateway or NAT instance allows outbound communication but doesn’t allow machines on the Internet to initiate a connection to the privately addressed instances.
For VPCs with a hardware VPN connection or Direct Connect connection, instances can route their Internet traffic down the virtual private gateway to your existing datacenter. From there, it can access the Internet via your existing egress points and network security/monitoring devices.
We are trying to avoid option #1 as there is a cost involved (along with complexity and security issues). #2 is the perfect resolution for us, but understanding the process to set it up has been eluding us for a while.
Can anyone walk us through what we need to do (or point us to the correct resources) to ensure the EC2 instance* can access the Internet by routing the traffic down the VPN, through our corporate datacenter, and our our existing Internet access point?
* and anything within the private subnet for that matter
If you are using scenario #2, then all there is to do on the AWS end is to ensure that traffic destined for the internet, 0.0.0.0/0 is routed to your Virtual Private Gateway.
Once traffic heads there, it will go to your Customer Gateway, and into your corporate datacenter. It's up to your local IT guys on that end to get Internet-destined traffic heading out, if it's even possible. But at that point, it's no longer an AWS issue.