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How to use AWS Elastic Load Balancing (ELB) withEC2?

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What is AWS Elastic Load Balancing (ELB)?

AWS Elastic Load Balancing (ELB) is a very useful service provided by Amazon. This

article will go through the uses of AWS ELB and how you can add and optimize virtual

machines using AWS Elastic Load Balancing (ELB).

The load balancer and Auto-scaling working are the same. Elastic Load Balancing (ELB)

automatically divides your incoming traffic in multiple instances, such as EC2 instances

and IP addresses, in one or more Availability Zones. ELB leads traffic to healthier

targets/instances. Elastic Load Balancing handles your load as your incoming traffic

changes over time. It can automatically scale to the majority of workloads.

But auto-scaling creates or terminates instances if our

given load increases or decreases.

Suppose we do not create a load balancer when users

search for data from our servers. The server will provide

data to the user. If some issues damage this server, then

we will lose all data. So that’s why we use a load balancer

on our servers.

How to use Virtual Machines with Elastic Load

Balancing (ELB)

We have created two virtual machines/servers. Now, we will create a load balancer after

the servers/virtual machines. When the user searches data from our servers, the first

request will go to the load balancer, and now the load balancer will check which server is

good and its load minimum. Then the load balancer will give the request to the minimum

load server, and after that, take data from this server and give a response to the user.

Now, if one server damages, then the load balancer will check which server is good, and

its load is low, then gives a request to this server and takes data from this server because

this server is also working and its load is also low. If you have also enabled auto-scaling,

then auto-scaling will create a new instance because one server has been damaged. After

creating the new instance, the load balancer will then distribute the load evenly between

both instances.

Types of Load Balancer

Four types of load balancer are available in AWS;

Application Load Balancer (created 2016)

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Network Load Balancer

Gateway Load Balancer

Classic Load Balancer (Previous Generation)

Application Load Balancer

AWS launched this load balancer in 2016. It is only used for Application software. It

works on the 7th layer of OSI. For example, suppose your task’s container definition

specifies port 80 for an NGINX container port and port 0 for the host port. In that case,

the host port is dynamically selected from the temporary port range of the container

instance (e.g. 32768 to 61000 on the latest Amazon ECS-optimized Amazon Machine

Image (AMI)).

ALB supports HTTP and HTTPS protocols.

Network Load Balancer

Network load balancer used for networking. It works on the 4th layer of OSI (Transport

Layer). For example, if your task container definition defines port 80 for the NGINX

container port and port 0 for the host port, dynamically move the host port from the

temporary port range of the container instance.

It supports TCP, UDP, and TLS protocols.

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Gateway Load Balancer

Gateway load balancers allow you to deploy and manage virtual tools, such as internet

firewalls, detection of interference and prevention systems, and deep packet inspection

systems.

Classic Load Balancer

It works on both the 4th and 7th OSI Model layers because this supports both layer’s

protocols. For example, load balancer port 80 can be mapped to container example port

3030 and load balancer port 4040 to container example port 4040.

It supports HTTP, HTTPS, TCP, and SSL protocols.

Load Balancer is always created in the

VPC. If you use many subnets, then

many availability zones are automatically

created.

Remember this:

1. Public IP is not assigned to each of

these instances; when we create a

Load balancer, then AWS assigns a

Public IP to the load balancer;

that’s why now incoming or

outgoing traffic will come and out

through the Load Balancer. Load

Balancer creates inside the VPC

and instances create inside the

subnet; that’s why incoming traffic, first of all, will go to the load balancer and load

balancer calls the instances. Private IP is assigned with each instance. The load

balancer can also use Private IP to give and take data from the instances.

2. As we know, the load balancer is connected to EC2-servers / instances but does not

use all incoming or outgoing traffic for the load balancer.

ELB Does not Support ICMP Protocol

If anyone can access data to these instances, but through the Ping/SSH/PUTTY, this

incoming traffic will not use the load balancer even though this request will directly go to

instance fetch data and then back response. Because the ICMP protocol is used for ping

commands and ICMP protocol is not used in the load balancer. That’s why the Ping

command will directly go to the instances.

But you can see Load Balancer only supports these protocols HTTP, HTTPS, TCP, UDP,

TLS, and SSL protocols. That’s why not all incoming or outgoing traffic use Load Balancer

if incoming or outgoing is coming from the Ping/SSH/PUTTY.

Now, we will discuss more 3-points

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Listener

Target Group

Target

Listener

Two types of listeners are as follows:

Front end listener

Backend listener

Both listeners are available around the Load balancer, but these listeners are always

invisible. We use a frontend listener to understand the user request. I mean the listener

will check user requests (which user requests are HTTP, HTTPS, TCP, or SSL), and when

the listener understands, it will send a request that relates to these servers or instances.

But make sure the frontend listener will not send a request to the direct EC2 instances

because these incoming requests are coming from the protocols. First, the Frontend

listener will send a request to the backend listener, and then the backend listener

sends a request to related servers for data.

If anyone wants to access data to these servers but through the Ping or SSH, this incoming

traffic will not use the load balancer even if this request will directly go to instance fetch

data and then back response. Because the ICMP protocol is used for ping commands and

ICMP protocol is not used in the load balancer. That’s why the Ping command will directly

go to the instances; not this will use a Load balancer.

Target Group

We can only 4-CIDR used in target IP. And these are fixed.

10.0.0.0/8

100.64.0.0/10

172.16.0.0/12

192.168.0.0/16

Which IP address Support ELB

Load balancer only supports IPv4. The load balancer can attach multiple availability

zones but only one subnet in one availability zone; if you choose another subnet, the last

subnet will be disconnected. 8 IP Addresses should always be available in ELB (Elastic

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Load Balancer).

How to manage load in each server

The load balancer always accesses through DNS, not the IP address. Load Balancer will

divide load in each availability zone. If one EC2 server is in one availability zone, the two

EC2 servers are in another availability zone, and the fourth EC2 servers are in the third

availability zone. Then the load balancer will divide the load in each availability zone.

For Example:

If your load is 100% in these availability zones, you know four EC2 servers are available in

this third availability zone, two in the second availability zone, and one in the first

availability zone. The load balancer will divide this load into these instances. Mean ELB

will divide this load into 33%, 33%, and 33% availability zones. You know four instances

are in the third availability zone, and now four instances will handle just this 33% load.

You also know one instance is available in one availability zone, and then this 33% load

will handle only one instance. That’s why this is not fair; we will use Cross Zone Load

Balancing because on one side, four instances are handling just 33%, and on another

side, just one instance handles 33% load.

Cross Zone Load Balancing

This type will distribute the load across each EC2 server, not into each availability zone.

For Example:

Total seven EC2 servers are available in these availability zones.

EC2 servers > 1+2+4 = 7

Load > 33.3%+33.3%+33.3% = 100%

100/7 = 14.28%

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This load is 14.28% that divides into each EC2 server/instance, not in the availability

zone. Suppose one EC2 server is in one availability zone. In that case, this will manage

only 14.28% load, in two EC2 servers are in the second availability zone, then this will

manage only 14.28%+14.28% = 28.56% load, and in four EC2 servers are in the third

availability zone, then this will manage 14.28*4 = 57.12% load.

This type works on the region and availability zone.

Read Also: How to Export/Import a MySQL database via SSH in AWS Lightsail

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