Elastic Load Balancer (ELB) Flashcards
What are the 3 different types of ELB available?
- Application Load Balancer ALB (HTTP/HTTPS)
- Network Load Balancer NLB (TCP/UDP)
- Classic Load Balancer CLB (Legacy)
What are the three components of ELB?
Listeners
Incoming traffic is evaluated against listeners. Listeners evaluate any traffic that is matches the Listener’s port. For Classic Load Balancer, EC2 instances are directly registered to the Load Balancer.
Eg. Port 80 or 443
Rules (Not avaliable for Classic Load Balancer)
Listeners will then invoke rules to decide what to do with the traffic. Generally the next step is to forward traffic to a Target Group
Target Groups (Not avaliable for Classic Load Balancer) EC2 instances are registered as targets to a Target Group
For Application Load Balancer (ALB) or Network Load Balancer (NLB), How does ELB work?
How is the flow? There are 6 steps
- xx.xx (Route 53)
- ALB or NLB
- Listeners: Listener Port 80
- Rule: redirect to Port 443
- Listener Port 443
- Rule: forward to Target 1 (EC2 instances)
For Classic Load Balancer (CLB) traffic is sent to the Listeners. When the port matches it then it forwards the traffic to any EC2 instances that are registered to the Classic Load Balancer. CLB does not allow you to apply rules to listeners.
How does it work? How is that flow? 4 steps…
- xx.xx (Route 53)
- CLB
- Listeners: Listener Port 80 and Listener Port 443
- Registered Targets
Which ELB component does incoming traffic hit first?
Listener
Which type of load balancers forwards traffic directly to EC2 instances without using a target group?
Classic Load Balancer
To associate an Application or Network load balancer with EC2 instances you must use one of these
Target Groups
This type of load balancer does not support creating rules on the listener
Classic Load Balancer
Application Load Balancers (ALB) are designed to…
Balance HTTP and HTTPS traffic.
What can you attach to an ALB?
Web Application Firewall (WAF)
Great for Web Applications
Which layer of the OSI model does an Application Load Balancer (ALB) operate on?
They operate at Layer 7 (of the OSI Model).
Layer 7 - Application Layer
The Application Load Balancer (ALB) feature that allows adding rules to a listener based on the HTTP protocol?
Request Routing
The host-based routing feature allows you to write rules that use the Host header to route traffic to the desired target group. T
Network Load Balancers are designed to…
balance TCP/UDP.
Which layer of the OSI model does a Network Load Balancer (NLB) operate on?
A Network Load Balancer (NLB) operates on the “Layer 4 - Transport Layer” of the OSI Model
Which type of load balancer is designed for optimum network performance?
Network Load Balancer
- Great for Multiplayer Video Games or When network performance is critical
A Classic Load Balancer (CLB) will throw this type of error when the underlying application is not responding.
504 Timeout Error
Not recommended for use, instead use NLB or ALB
Clasic Load Balancer
It was AWS first load balancer (legacy)
Sticky Sessions will ensure that …
All traffic from a session is sent to the same EC2 instance
What do Sticky Sessions use in order to remember EC2 instances for a session?
Cookies
Advanced load balancing method that allows you to bind a user’s session to a specific EC2 instance.
əˈlaʊz
Typically utilized with a Classic Load Balancer
ˈtɪpɪkli
Can be enabled for ALB though can only be set on a Target Group not individual EC2 instances.
Sticky Sessions
The X-Forwarded-For header contains what information about a user?
Their IPv4 Address
If you need the IPv4 address of a user, check the X-Forwarded-For header
The X-Forwarded-For (XFF) header is a command method for identifying the originating IP address of a client connecting to a web server through an HTTP proxy or a load balancer.
For an ALB or NLB where would you configure health checks?
On the target group
Instances monitored by ELB health checks report back either of these 2 statuses
ˈstætəsɪz
InService or OutofService
Cross-Zone load balancing is only possible using these 2 types of load balancers
- Classic Load Balancer (CLB)
- Network Load Balancer (NLB)
IN ELB, Cross-Zone Load Balancing Enabled.
Requests are …
… distributed evenly across the instances in all enabled Availability Zones.
Evenly = in equal numbers, amounts, or values.
AZ1, 2 instances: 10% each one
AZ2, 4 instances 10% each one
IN ELB, Cross-Zone Load Balancing Disabled does what?
Requests…
… are distributed across the instances in only its Availability Zone.
dɪˈstrɪbjətəd
AZ1, 2 Instances: 50% each one
AZ2, 4 instances: 25% each one
In ELB, Apply rules to incoming request and then forward or redirect traffic.
(What is the name of the feature)
ELB Request Routing
In ELB, What 6 conditions can you use to route your traffic?
✔️ Host header ✔️ Source IP ✔️ Path ✔️ Http header ✔️ Http header method ✔️ Query string
How many AZs does an ELB have to have?
At least 2
What can you attach to an ALB for SSL?
Amazon Certification Manager SSL
What is ELB?
What are its 4 topics?
- It’s a service that automatically distributes incoming application traffic across multiple targets, such as Amazon EC2 instances, containers, IP addresses, Lambda functions, and virtual appliances.
- Types (Network, Application and Classic)
- Components (Listeners, Rules and Target Groups)
- Attachable elements (WAF, Certificate Manager SSL)
- Sticky Sessions
