I have a simple question, If I use an internet-facing NLB wouldn't it be accessible on the internet, by that I mean, the NLB URL can be directly accessible from the internet. How can I restrict that . I don't want my NLB to be accessed from the internet.
My EC2s have SG 0.0.0.0/0 to allow all traffic and EC2s are in private subnets. NLB in public subnet.
Any help please?
I don't want my NLB to be accessed from the internet.
You could have used internal facing NLB for this. But since this is already done, you can allow only people from your org to access it over https & whitelisted IPs.
My EC2s have SG 0.0.0.0/0 to allow all traffic and EC2s are in private subnets
For EC2, allow all or required traffic only from SG of NLB. This way your NLB gets traffic from internet while EC2 gets only from NLB SG
Related
I have 4 EC2 instances, 2 in the private subnet of each availability zone (2AZs), one hosting App A and the other hosting AppB. The instances are behind 2 internet-facing ALBs (one ALB for each app), with route 53 routing the traffic to the corresponding ALB based on the sub-domain name, and 2 NAT Gateways in each public subnet routing internet traffic for the private instances.
I want appA and AppB to communicate using HTTPs using the domain name of each app.
Will the traffic for each Application come from the load balancer? Since each EC2 instance allows the traffic only from the security group of its ALB.
Should the security group for each app allow the traffic from the other or the traffic will come from the load balancer?
I have DNS resolution activated for the VPC.
For traffic within the setup you've described the ingress traffic for the domains will enter through the load balancer which will then forward the requests to the EC2 instance(s). As long as the load balancers security group allows the inbound traffic you will receive the traffic.
For egress traffic for your application it will depend on both your EC2 and routing configuration.
If your EC2 instance resides within a public subnet (and has a public IP address) then the EC2 will route traffic via the internet gateway. If your EC2 instance is in a private subnet you will need to use either a NAT Gateway or NAT instance to route traffic to the internet.
These options will be configured within the route table for the subnet(s) that are applicable, in addition the outbound security group rules for your EC2 instance will need to allow access to the destination ip, port and protocol that you want. By default the security group will allow all outbound access.
We have Typical 3 tier architecture having Web, App and DB.
Can we make EC2 instances in the web tier as Private? and allow incoming traffic only through ALB?
AFAIK we can apply an SG only allowing connections from the SG of the ALB. But What if our Private EC2 instance has to return response back to the client? How it'll be routed through ALB as ALB is mostly used for managing incoming traffic.
Also for outgoing traffic can we configure something like Private EC2 instance -> ALB -> Internet? If yes then how? So, is there any way for private EC2 instances to communicate to internet without assigning them public IP?
But What if our Private EC2 instance has to return response back to the client? How it'll be routed through ALB as ALB is mostly used for managing incoming traffic.
You don't have to do anything special, assuming your ALB and instances are correctly set. Any request coming to ALB, will be able to return to the client event if instances are in private subnet without any internet connectivity.
However, your instance won't be able to initiate internet connections by themselves. So if the instances don't need internet to operate, you don't need NAT. Otherwise, it is required.
Keeping your instances in a private subnet is best practice, even for the web layer.
For inbound traffic you would add a load balancer into your public subnets then allow HTTP/HTTPS ingress on the webs security group only from the load balancer. You can either do this through adding the subnet ranges into the web servers security group, or reference the security group the load balancer has assigned to it instead.
For outbound internet traffic in a private subnet you will need to create either a NAT Gateway or NAT instance within a public subnet, and then add a route for 0.0.0.0/0 for the private subnet to route traffic to the NAT. Additionally if you want IPv6 traffic you would create an egress only internet gateway with a route of ::/0.
I have configured a cloud with following configuration
VPC with a public and private subnet in two availability zones. Public subnet has an internet gateway and private subnet has a NAT gateway configured
An internet-facing Network Load Balancer allowing TCP traffic configured in both availability zones
A target group to forward traffic from the load balancer
An EC2 instance in private subnet configured with haproxy listening at port 80. It's security group is configured to accept TCP traffic at port 80 from both the subnets in which NLB is configured
Added this instance to the target group, the status is healthy
When I try to hit the NLB DNS it is giving me 'Connection timed-out' error. I am expecting that when I hit NLB DNS it should forward me to the private instance. I have checked many AWS documents such as this link but still cannot find the resolution to this issue. Please feel free to ask for more information if this is not sufficient.
It's security group is configured to accept TCP traffic at port 80 from both the subnets in which NLB is configured
When targets are registered by instance-id, the security group for instances behind an Internet-facing NLB need to allow traffic from 0.0.0.0/0 -- or whatever range of public IP addresses need to access them through the balancer -- not just the subnets of the balancer (which are needed for health-checks).
If your target type is an instance, add a rule to your security group to allow traffic from your load balancer and clients to the target IP.
https://aws.amazon.com/premiumsupport/knowledge-center/security-group-load-balancer/
Unlike ALB and Classic balancers, NLB traffic has the source address of the external client when the targets are configured by instance-id, and this is the address the security group is matching against.
Our aim is to get our Elastic Beanstalk setups to route traffic through a NAT gateway as we require for certain traffic connecting to API's which require IP whitelisting. Rather than make modifications to the current setup, I have created a separate/isolated VPC & EC2 instance to familiarise and test the setup. However I am yet to get the setup working as desired.
Here is the setup
VPC (vpc-77049811) with CIDR of 10.0.0.0/16
Internet gateway (igw-4d4b212a) assigned to mentioned VPC
Subnet (subnet-096d8a53) with CIDR of 10.0.1.0/24
NAT Gateway (nat-00bb49204627de7e6) attached to mentioned subnet and assigned Elastic IP
Route table attached to mentioned VPC and associate with mentioned subnet
1x EC2 Instance assigned to VPC and its own Elastic IP and Disabled Source/Destination Check
Route Table Setup
10.0.0.0/16 local
0.0.0.0/0 igw-4d4b212a
With the above setup, and am able to log into the server and make a curl request to get the servers public IP address (curl icanhazip.com). As soon as I add a rule to the route table for the url's resolved IP's to route through the NAT gateway though, I am unable to ping or request the curl request as it will timeout.
Rules added to route table which do not work
45.63.64.111/32 nat-00bb49204627de7e6
144.202.71.30/32 nat-00bb49204627de7e6
Not sure if I've overlooked something here or maybe I have misunderstood the concept and use cases for the NAT gateway?
This is public IP 45.63.64.111. You need IGW to reach to this traffic.
You either do that by directly redirecting your traffic to IGW
OR
You do that by directing to NAT then further directing that traffic to IGW
Directing to IGW part is missing.
Nat gateway is used for EC2 in private subnets (which does not have IGW attached to it). In scenario above, EC2 is in public subnet so ideally it does not need NAT.
Here is what I would do to use NAT-
1. Place EC2 in private subent. and have a Route table where all outgoing traffic to nat-gateway.
2. Nat-gateway which is in public subnet will forward your traffic to IGW.
It seems like you have misunderstood the purpose of a NAT.
Its purpose is to provide outbound internet access to instances in a private subnet without allowing any inbound connectivity - i.e. a subnet where the routing table does NOT have an entry for:
0.0.0.0/0 igw-4d4b212a
If you want to restrict access from your EC2 instance to specific IP addresses, put your NAT in the public subnet, create a private subnet, and put your instance in the private subnet. Then add the two routes to the route table associated with the private subnet:
45.63.64.111/32 nat-00bb49204627de7e6
144.202.71.30/32 nat-00bb49204627de7e6
If you simply want to restrict access of your EC2 instance to a couple of IP addresses, you can only create routes for those addresses:
45.63.64.111/32 igw-4d4b212a
144.202.71.30/32 igw-4d4b212a
Be aware that with this last option, your instance can be reached from the internet if you have rules open in your security groups.
I'm putting the instances behind the aws loadbalancer, I have configured the routable and attached the IGW to it, created the loadbalancer and added this instance to the aws loadbalancer every things work well, the endpoint URL of the AWS loadbalancer able to load the HTTP pages
Now i have removed the IGW from the route table and tested it again, the AWS loadbalalncer endpoint URL not able to load the page, but the instace status shows in AWS loadbalancer as inService
Why the IGW is required when loadbalancer is configured over private subnet, it technically Mean it's a public subnet, which is blocking me to create a NAT inatance
A subnet without a default route pointing to the igw-xxxxxxxx Internet Gateway object is, by definition, a private subnet. If you remove the igw from a public subnet, you now have a private subnet.
Placing an Internet-facing load balancer (ELB) in such a private subnet is incorrect.
It sounds as though you are making a commonly-made -- but incorrect -- assumption that the ELB should be configured in the same subnets as the instances behind it. This is also incorrect.
Provision the ELB in public subnets, without regard to the subnets the instances behind it were placed in.
In summary:
Internet-facing ELB requires a public subnet for placement.
NAT instance requires a public subnet for placement.
The instances that use these services (NAT and ELB) belong in different -- private -- subnets, different subnets than the ELB and NAT instances.
ELB and NAT can be placed together in the same subnets, or separately, as long as the subnets are public (have the IGW as their default route) and are in the same availability zones.
I believe you cannot do anything without the IGW attached to the routing table where the subnet is attached to.
Another way to do this is to spin off a NAT instance(can be found in AWS marketplace) in the public subnet, add it to your private route table where your original instance is on (0.0.0.0/0 - instanceid) all the traffic will be routed through the NAT instance.
Here mainly we have to see two things, provided subnet for the elasticloadbalancer is public or private.
Every VPC should have one IGW to connect to the public, every trafic should go through the IGW only. If VPC connected to the IGW, IGW distribute internet to the all instance which are in that VPC, if route table changed to the particular rt, internet traffic can send to only that instance. Here in ELB instance is in service because both are in the same VPC and can communicate each other means checks the status. This IGW will work main role when we are using the NAT.
Always we provide ip range for the IGW or rt as 0.0.0.0/0, it represents as public.
The following link will explain more : http://docs.aws.amazon.com/AmazonVPC/latest/UserGuide/VPC_Scenario2.html
This small explanation might be helpful for someone.
Let me cover your two questions
the AWS loadbalalncer endpoint URL not able to load the page, but the instace status shows in AWS loadbalancer as inService
This is the default behaviour of load balancer , since internally load balancer and your instance may be in the same VPC so they are able to communicate that is why loadbalancer is showing inService status.
Second question Why the IGW is required when loadbalancer is configured over private subnet, it technically Mean it's a public subnet, which is blocking me to create a NAT inatance
You need IGW if you want to access any resources especially EC2 , Loadbalancer from internet. however if you put your load balancer in private subnet it means IGW is not associated with the subnet having loadbalancer in it and hence this load balancer is not accessible outside your VPC that is reason that you were not able to load your page.
NAT instance is usually used when you want your private subnet instances should be able to initiate request over internet and has nothing to do with normal load balancing setup unless and untill you want dont want to install any updates from internet to your instance.
You are trying to access webpage publicly and removing the route entry IGW from the loadbalncer subnet.
The Subnet without IGW will become Private, Hence you can't access it.
First, a subnet with route table that route traffic via the internet gateway (IGW) is a public subnet. An IGW is required because the subnets created in AWS VPC are internal IPs and as internal IPs are not routable via the internet, traffic to and fro EC2 instances that belongs to an internal IP needs a way to complete these request. This is where an IGW comes into play. The IGW allows your EC2 instance to make outbound request to the internet and allows other user/client to make inbound request to your ec2 instance.
A public subnet are group of IPs (called subnets) in your VPC that allows internet traffic to and fro your ec2 instance. A subnet without an Internet gateway is a private subnet. As you already guess no traffic is allowed in or out.
That said, instances in VPC which are in Private subnet still need to initiate an outbound request to the internet to download software or perform update. In this case you have to create and attach a NAT gateway or NAT instance to the private subnet. NAT Gateway and NAT instance only allow outbound traffic to the internet but not the the other way round. In some cases you might want your production EC2 to be in the private subnet and ELB in public subnet for security reason.
ELB usually belong to the public subnet so it reachable from the internet as is your case as well.
TO answer some of your question - when you deleted the IGW from the route table, your ELB automatically becomes a private subnet as such your web page stops loading.
Also, you could still see the ec2 instance behind the ELB as InService even when you deleted the IGW because the ELB and EC2 instance can communicate via the internal IP as they are in same network or VPC.
The ELB needs a route to the internet in order to send you the response over internet.. As simple as that.
Configure your ELB in public subnet, regardless of where your instances are present.
Basically there are two types of load balancers.
1)Internal
2) External
Internal load balancers are those which are launched in a private subnet which will be accessible only internally by the instances on same vpc of the internal elb
External load balancers are which are accessible over the internet which should be launched in a subnet which has internet gateway attached to it and which has route table configured properly to route the requests.
If you attach an internet gateway to a subnet it becomes a public subnet.Also if you create a load-balancer which you need to be accessible from internet it should be a External load balancer and aws will not allow it launch in a private subnet.The instances are showing in service because its communicating internally using private ip-address.