DAY4-AWS-CSA

1] What is IP address

An IP address, or Internet Protocol address, is a unique number that identifies a device on the internet. IP addresses are used to send and receive data between devices on a network.?

How IP addresses work

• IP addresses are assigned by an internet service provider (ISP).?
• They are calculated and distributed by the Internet Assigned Numbers Authority (IANA).?
• IP addresses are similar to a physical address for a home or business.?
• IP addresses are used to route data packets to the correct destination.?

IP address types

• There are two main versions of IP addresses: IPv4 and IPv6.?
• IPv4 addresses are 32 bits long and use a numeric string.?
• IPv6 addresses are 128 bits long and use an alphanumeric string.?
• There are also different types of IP addresses, including public, private, static, and dynamic

2] what is public IP address ?

A public IP address in AWS is an IP address that is accessible over the internet. AWS assigns public IPs to resources like EC2 instances to enable communication with the outside world. There are two types of public IP addresses in AWS.

1. Elastic IP (EIP)

• A static public IP that you can allocate and associate with an EC2 instance.
• Remains the same even if the instance is stopped and restarted.
• Useful for ensuring a consistent IP for external applications or services.
• You are charged if the Elastic IP is not associated with any instance.

2. Auto-Assigned Public IP

• A dynamic public IP assigned when an EC2 instance is launched in a default VPC.
• Changes if the instance is stopped and started.
• AWS assigns it automatically, but you cannot reassign or reserve it.
• Not assigned by default in a custom VPC unless explicitly configured.

3] What is Private IP address ?

A private IP address in AWS is an IP address assigned to an instance within a VPC (Virtual Private Cloud) that is only accessible within the AWS network. It is not reachable over the public internet.

Key Features of a Private IP Address:

1. Internal Communication: Used for communication between instances within the same VPC or AWS services (e.g., databases, applications).
2. Persistent: The private IP remains the same for an instance, even if it is stopped and restarted.
3. Assigned from a Subnet CIDR Block: Each EC2 instance gets a private IP from the CIDR range of the subnet it is launched in.
4. Multiple Private IPs: An instance can have multiple private IPs if multiple network interfaces (ENIs) are attached.
5. No Direct Internet Access: Private IPs cannot communicate with the internet unless a NAT Gateway or Elastic IP (EIP) with public IP is used.

4] Private IP Vs Public IP address

Example Scenario

• Private IP: Used for backend servers, databases, and microservices inside AWS that don’t need direct internet access.
• Public IP: Used for web servers, application servers, or services that require public access.

5] EC2 placement groups

A Placement Group in AWS is a way to control the placement of EC2 instances to optimize network performance, reduce latency, or increase fault tolerance

Types of Placement Groups:

1. Cluster Placement Group
2. Spread Placement Group
3. Partition Placement Group

Cluster Placement Group

• Places instances close together in a single Availability Zone (AZ).
• Best for: High-performance computing (HPC), low-latency applications.
• Limitation: If hardware fails, all instances in the group may be affected.

Spread Placement Group

• Distributes instances across multiple hardware racks within one or more AZs.
• Best for: Critical applications needing high availability (e.g., database servers).
• Limitation: Only up to 7 instances per AZ.

Partition Placement Group

• Divides instances into partitions to isolate failures.
• Best for: Big data workloads like Hadoop, Cassandra, and Kafka.
• Limitation: Limited to max 7 partitions per AZ.

6] Elastic network interface

An Elastic Network Interface (ENI) is a virtual network card in AWS that can be attached to an EC2 instance, allowing it to communicate within a VPC (Virtual Private Cloud).

Key Features of ENI:

1. Primary and Secondary ENIs
2. Multiple IP Addresses
3. Detachable and Reusable
4. Security Group & Routing Control
5. Traffic Mirroring & Monitoring

Primary and Secondary ENIs

• Every EC2 instance has a primary ENI (default).
• You can attach additional secondary ENIs for multiple IP addresses.

Multiple IP Addresses

• An ENI can have one primary private IP and multiple secondary private IPs.
• You can also attach a public IP or Elastic IP (EIP) to an ENI.

Detachable and Reusable

• ENIs can be moved between instances, unlike instance-specific network interfaces.
• Useful for maintaining network configurations when switching instances.

Security Group & Routing Control

• ENIs support Security Groups and Network ACLs, providing network security.

Traffic Mirroring & Monitoring

• Supports VPC Traffic Mirroring for monitoring network traffic.

7] What is EC2 Hibernate?

EC2 Hibernate is a feature that allows you to pause and resume your Amazon EC2 instances without losing in-memory data. It works similarly to the hibernate function on a laptop—saving the RAM contents to disk and restoring them when the instance restarts.

How EC2 Hibernate Works

1. Saves Memory to Disk When hibernating, AWS writes the contents of RAM to the root volume (EBS).
2. Stops the Instance The instance enters a Stopped state (instead of being terminated).
3. Restores on Restart When restarted, AWS loads the saved RAM data back into memory, restoring the session as it was before hibernation.

Benefits of EC2 Hibernate

? Faster Startup – No need to reboot and reload applications.

? Session Persistence – Apps remain open and in the same state.

? Cost Savings – No compute charges while hibernated (only storage costs for RAM data).

? Security – The memory snapshot is encrypted.