Using AWS services - I have used VPC and divided it into two subnets(private and public), then created two route tables(private and public), created one Internet gateway and attached to the public route table and one NAT Gateway connected to the private route table also both the route tables are mapped to their respective subnets but the problem is I need to deploy some code in the ec2 instance whose IP should not go without touching NAT Gateway.
I had many articles and also followed youtube but still I am very much confused like how to achieve this and whatever I did is right or wrong.
Also NAT gateway should be attached in private or public?
Also NAT gateway should be attached in private or public?
NAT should be deployed in public subnet. Then for your private subnet, you setup a route to the NAT.
Once this is done, you place your EC2 instance in the private subnet. This way, any internet traffic from the instance will be routed through the NAT.
Related
Can I download and install patches from Internet using Route53, without having NAT Gateway and IGW?
I think you might be a little confused regarding what Route53 is:
Amazon Route 53 is a highly available and scalable cloud Domain Name System (DNS) web service.
Source
So, it has nothing to do with downloading patches. You can use it to handle your domains, and it can work nicely with several AWS services.
Now, regarding your question. If you want an EC2 instance to access the Internet and download its security patches, you will need an Internet Gateway configured on the VPC of the instance. On the other hand, the NAT Gateway is only necessary if your instance is configured on a private subnet. A private subnet doesn't have direct access to the Internet Gateway, so you need to provide a NAT Gateway to allow your instances to reach it. EC2 instances in public subnets can be assigned public IPs. An instance with a Public IP can access the Internet directly through the Internet Gateway without needing a NAT Gateway.
Another resource you are going to have to configure is Route Tables. Each subnet is assigned to a single Route Table. Once attached, it will use the routes define on the Route Table to handle their instances traffic. A Route Table that handles private subnets will have a default route pointing to a NAT Gateway. And a public Route Table will have a default route pointing directly to the Internet Gateway. Bear in mind that the NAT Gateway should always be instantiated on public subnets.
Take a look at the following documentation site for more information:
VPC Internet Gateway
VPC Subnet
VPC Route Tables
Route53 is a DNS service and its function is DNS resolution. You need NAT Gateway for outbound internet access from private subnet
Hope you are all doing good.
AWS allows us to attach a private subnet (created in a Customer VPC) with a route table having route to the internet via internet gateway. Does it make any difference to the instance launched in the private sub-net? or it is as good as having the private subnet not linked to the route table having route to the internet
Regards
AJ
A subnet is not private if it has routes to/from the internet. The instances launched in a private subnet cannot access the internet and cannot be reached from the internet.
For e.g if you have a database instance and you don't want anyone but the instances to access the instance, you can launch the instance in the private subnets.
Also if you want the instances in the private subnet to access internet, you need to setup a Nat Gateway (or a Nat Instance)
Hope this helps
First, we need to know what's the difference between a public subnet and a private subnet.
Public Subnet means this subnet has an Internet Gateway attached to it.
Private Subnet means this subnet has a NAT Gateway attached to it.
And the Internet Gateway can have both inbound and outbound but the NAT only can have outbound to the Internet.
And A NAT will be built in a public subnet but attach to a private subnet.
You can have lots of public/private subnets at the same time and attached NAT or IGW for them, but the IGW only can have one in each VPC.
In some use cases, we will not attach any kinds of NAT and IGW for a subnet. that's because it might be a database subnet and won't expect it to communicate with the Internet.
Normally, we will use a subnet with NAT attached for our application such as EC2 or ECS, Internal Load Balancers.
On the other hand, we will use a subnet with IGW attached for Internet-facing Load balancers, Nginx, Apache.
AWS VPC Design:
https://aws.amazon.com/tw/answers/networking/aws-single-vpc-design/
I think the hidden magic here is that the instance in the private subnet needs a public IP to communicate with outside, we never ever think this an issue in our lives. When our computer connect to the router, it get access to internet without any issue, why it works so smoothly? All because the router handles everything for us, including allocating a private IP for us, making recursively DNS query for us, and the most important, translating the private IP using the router's public IP so that our computer can communicate with the outside bidirectionally.
Let's go back to this AWS VPC scenario, you attached a route table with a default route to the Internet Gateway to your private subnet, which makes it looks like a public subnet. However, the instances still have no public IPs, and, not like our router, the Internet Gateway of AWS VPC doesn't do NAT works! So how can an instance with no public IP and no NAT access the internet? It's impossible.
The link explains that need to use NAT Gateway for the public subnet to make it possible to access the internet and the lambda function access the RDS instance. First does it realy have to be NAT Gateway can't use instead a Internet Gateway for that purpose?
Second have two Route Tables one named PublicNetwork that haves two subnets and the route haves one Internet Gateway,
the second Route Table that haves only one subnet called PrivateNetwork.
when had only one Route Table with all 3 subnets could access the rds (db) instance with Microsoft SQL Server Management (security group with inbound rules of type MS SQL and Source my ip address) now with the changes can't access anymore.
My database in RDS haves in Subnet group my default-vpc that haves the 3 subnets is it needed to create another vpc and transfer the private subnet to it to be able to access my database again?
All subnets in a VPC can communicate with each other
An Internet Gateway connects the VPC to the Internet
Any subnet that has a Route Table pointing 0.0.0.0/0 to the Internet Gateway is called a Public Subnet (because it can directly communicate with the Internet)
Any subnet that does not have such a Route table entry is called a Private Subnet
If a resource in a private subnet needs to communicate with the Internet, it must send the network traffic via a NAT Gateway in the Public Subnet. The NAT Gateway will forward the traffic to the Internet, then return any response that is received.
If you are having difficulty connecting to resources within the same VPC, then the Security Group is the most likely cause of the problem.
I have a AWS Lambda function which:
checks a Redis Elasticache instance,
if the item is not found in the cache, goes to Google Places API service.
The Redis instance is in a private subnet; so, to fetch it, I added the VPC and the subnet in which the instance resides. I also specified the security group which allows all the outbound traffic. The Network ACL is the default one which is supposed to all the inbound and the outbound traffic.
When adding VPC to Lambda function like that via the console, it prompts:
When you enable VPC, your Lambda function will lose default internet access. If you require external internet access for your function, ensure that your security group allows outbound connections and that your VPC has a NAT gateway.
So, in the Route Table of the private subnet, I added a NAT gateway too. However, at the point where the Google Places API service call is made from the Lambda function it is always doomed to result in timeout.
In short, I doubt that the NAT gateway properly allows internet access of the Lambda function. How can I check what goes wrong with it?
Do NAT Gateways log the calls or the call attempts being tried through it somehow in CloudWatch etc.?
I want to elaborate on the answer from #vahdet. I was losing my mind trying to reconcile how the NAT Gateway was supposed to be in the public and private subnets simultaneously. It seemed like the official AWS documentation here was wrong, but of course it's not. There is a very subtle detail that myself and others have missed.
The NAT Gateway has to be "hot-wired" across two different subnets simultaneously in order to bridge private addresses to a public one that is internet facing.
First, I tried to put the NAT Gateway in the same route table as the IGW, but of course that doesn't work because you can't have two identical routes (0.0.0.0/0) with different targets.
The guide was saying to put the NAT Gateway in the route table for the Private Network, which I did, but that didn't seem to work.
The critical detail I was missing was that the NAT Gateway has to be created in a public subnet. The documentation actually says this, but it seems confusing because we are later told to put the route for NAT Gateway in the private table.
Both things are true. Create the NAT Gateway in the public subnet and then only add a route table entry in the private route table.
The documentation tells you to create the following network resources in the VPC:
two new subnets
two new route tables
one new NAT Gateway
I already had a route table and some subnets, so I tried to only add one new subnet and one new route table and this is where I got into trouble. It really was better to create two of each as documented.
Here's what it the subnets look like for me:
subnet-public 10.8.9.0/24 us-east-1a
subnet-private 10.8.8.0/24 us-east-1a
Then create the NAT Gateway in subnet-public.
It will be pending for a couple of minutes, which is important, because it must go to available status before it can be referenced in a route table entry.
Here are the route tables:
route-table-public
10.8.0.0/16 local
0.0.0.0/0 igw-xyz
subnet-association: subnet-public
route-table-private
10.8.0.0/16 local
0.0.0.0/0 nat-abc
subnet-association: subnet-private
Do you see what happened there? It's really subtle. The NAT Gateway is cross-wired. It "lives" in the public subnet it was created in, but all traffic in the private subnet gets routed to it.
If you create the NAT Gateway in the private subnet like I did at first, then the NAT Gateway is just as isolated as everything else in the private subnet, and has no way to route traffic out to the internet. It must be created in the public subnet to have internet access, because it must have an IP address inside the public subnet. My NAT Gateway got an internal IP of 10.8.9.127 and an external IP in the 54.X.X.X range.
By making the NAT Gateway the 0.0.0.0/0 route in the private routing table, we are telling all non-10.8.0.0/16 traffic to go straight to the NAT Gateway, even though it isn't actually inside the private subnet.
The VPC itself knows how to bridge traffic across its own subnets, and is able to send the 10.8.8.X traffic to the NAT Gateway's 10.8.9.X IP. It then acts as a bridge, and translates all of that traffic across it's internal IP to its external IP. Because it is in a public subnet that is in a route table with an internet gateway, the external IP has a clear path to the internet.
Now my private VPC lambda in subnet-private has verified internet access through the NAT Gateway.
The following steps are required
An IAM role with full VPC permission assigned to your lambda function.
VPC with public and private subnet
while creating a NAT Gateway
a)the subnet has to be public subnet
b)Elastic IP creat a new one or allocate one
Create the route table and add another route with target as our NAT gateway we created above.
And your lambda should be happy now
The problem for my case turned out to the fact that, I had created the NAT Gateway in the private subnet.
Make sure you place the NAT Gateways in the public subnet.
By the way, there are metrics but no direct logging records available in CloudWatch for NAT Gateway.
Im working on building up my network which consists of a subnet in a VPC and three instances in the subnet. I have an elastic IP on one of the instances and no public ip or DNS on the others. For the purpose of the other instances reaching the internet for things like windows updates, is it possible to associate a public IP with the internet gateway on the VPC so all of the instances can reach the internet through one IP and for incoming traffic it would all be routed to Instance 1 only on a certain port. In our office now we have a server with multiple vlans all communicating to the internet with one public IP and i am trying to replicate this.
Thanks in advance for the help!
I did some searching before writing out the whole answer and found this write up that should help give you an idea on the distintion between an internet gateway and a Nat gateway. This will help with what you're trying to accomplish:
AWS VPC - Internet Gateway vs. NAT
As other have posted: using a NAT gateway is the best option here since instances with private ips will be able to connect to the internet.
If you do have instances that are "public" ie with and EIP and others that should be private, I would recommend this architecture as laid out in the vpc guides on aws:
https://docs.aws.amazon.com/AmazonVPC/latest/UserGuide/VPC_Scenario2.html
This will give you a good logical separation between public and private servers since they will be within their own subnet.
NAT Gateway might be able to solve this for you.
You need to split your design into "public" and "private" subnets.
Create a new subnet. In this subnet add a NAT Gateway. Add a default route to the NAT Gateway. Then move the instances that you want private into the private subnet.
For the public subnet, just have the instances that you want to be public on the Internet.
The other suggestions about adding a NAT Gateway to your existing subnet won't work. You would need two default routes (one for the Internet Gateway and the other for the NAT gateway).
Keep in mind that the Internet Gateway is a special type of NAT Gateway. This is why you should not have have both in the same subnet (not without knowing what you are doing with route tables in both the VPC and the instances).