AWS Interview Questions

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1. What Is Amazon Virtual Private Cloud (amazon Vpc)?

Amazon VPC lets you provision a logically isolated section of the Amazon Web Services (AWS) cloud where you can launch AWS resources in a virtual network that you define. You have complete control over your virtual networking environment, including selection of your own IP address range, creation of subnets, and configuration of route tables and network gateways. You can also create a hardware Virtual Private Network (VPN) connection between your corporate datacenter and your VPC and leverage the AWS cloud as an extension of your corporate datacenter.

 You can easily customize the network configuration for your Amazon VPC. For example, you can create a public-facing subnet for your web servers that have access to the Internet, and place your backend systems such as databases or application servers in a private-facing subnet with no Internet access. You can leverage multiple layers of security, including security groups and network access control lists, to help control access to Amazon EC2 instances in each subnet.

2. What Are The Connectivity Options For My Vpc?

You may connect your VPC to:

 The Internet (via an Internet gateway)

Your corporate data center using a Hardware VPN connection (via the virtual private gateway)

Both the Internet and your corporate data center (utilizing both an Internet gateway and a virtual private gateway)

Other AWS services (via Internet gateway, NAT, virtual private gateway, or VPC endpoints)

Other VPCs (via VPC peering connections)

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3. How Do You Connect My Vpc To The Internet?

Amazon VPC supports the creation of an Internet gateway. This gateway enables Amazon EC2 instances in the VPC to directly access the Internet.

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4. What Are The Components Of Amazon Vpc?

Amazon VPC comprises a variety of objects that will be familiar to customers with existing networks:

 

A Virtual Private Cloud (VPC): A logically isolated virtual network in the AWS cloud. You define a VPC’s IP address space from a range you select.

Subnet: A segment of a VPC’s IP addresses range where you can place groups of isolated resources.

Internet Gateway: The Amazon VPC side of a connection to the public Internet.

NAT Gateway: A highly available, managed Network Address Translation (NAT) service for your resources in a private subnet to access the Internet.

Hardware VPN Connection: A hardware-based VPN connection between your Amazon VPC and your datacenter, home network, or co-location facility.

Virtual Private Gateway: The Amazon VPC side of a VPN connection.

Customer Gateway: Your side of a VPN connection.

Router: Routers interconnect subnets and direct traffic between Internet gateways, virtual private gateways, NAT gateways, and subnets.

•Peering Connection: A peering connection enables you to route traffic via private IP addresses between two peered VPCs.

VPC Endpoint for S3: Enables Amazon S3 access from within your VPC without using an Internet gateway or NAT, and allows you to control the access using VPC endpoint p

LI>Egress-only Internet Gateway: A stateful gateway to provide egress only access for IPv6 traffic from the VPC to the Internet

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5. What Are The Steps To Build A Custom Vpc?

Below are the steps of build a custome VPC:

 Create a VPC

Create subnets

Create an internet gateway (IGW)

Attach the new IGW to your VPC

Create a new route table (RT)

Add the IGW as a route to the new RT

Add a subnet to the RTs subnet associations (this will be the public facing subnet)

Create web server (public subnet) and database server (private subnet) instances

Create a new security group for the NAT instance

Add HTTP and HTTPS inbound rules that allow traffic from the private subnets IP

Create a NAT instance (public subnet).

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Diable Auto-assign Public IP.

Add it to the NAT security group

      12. Create an Elastic IP

      13. Associate the Elastic IP to the NAT

      14. Disable Source/Destination Checks for the NAT

      15. Add the NAT instance as a route to the initial VPC RT

6. Why Should You Use Amazon Vpc, Advantage Of Using Aws Vpc?

Amazon VPC enables you to build a virtual network in the AWS cloud - no VPNs, hardware, or physical datacenters required. You can define your own network space and control how your network, and the Amazon EC2 resources inside your network, is exposed to the Internet. You can also leverage the greatly enhanced security options in Amazon VPC to provide more granular access both to and from the Amazon EC2 instances in your virtual network

7. What Is The Difference Between Stateful And Stateless Filtering?

Stateful filtering tracks the origin of a request and can automatically allow the reply to the request to be returned to the originating computer. For example, a stateful filter that allows inbound traffic to TCP port 80 on a webserver will allow the return traffic, usually on a high numbered port (e.g., destination TCP port 63, 912) to pass through the stateful filter between the client and the webserver. The filtering device maintains a state table that tracks the origin and destination port numbers and IP addresses. Only one rule is required on the filtering device: Allow traffic inbound to the web server on TCP port 80.

 Stateless filtering, on the other hand, only examines the source or destination IP address and the destination port, ignoring whether the traffic is a new request or a reply to a request. In the above example, two rules would need to be implemented on the filtering device: one rule to allow traffic inbound to the web server on TCP port 80, and another rule to allow outbound traffic from the webserver .

8. Can Amazon Ec2 Instances Within A Vpc Communicate With Amazon Ec2 Instances Not Within A Vpc?

Yes. If an Internet gateway has been configured, Amazon VPC traffic bound for Amazon EC2 instances not within a VPC traverses the Internet gateway and then enters the public AWS network to reach the EC2 instance. If an Internet gateway has not been configured, or if the instance is in a subnet configured to route through the virtual private gateway, the traffic traverses the VPN connection, egresses from your datacenter, and then re-enters the public AWS network.

9. Why Can’t You Ping The Router, Or My Default Gateway, That Connects My Subnets?

Ping (ICMP Echo Request and Echo Reply) requests to the router in your VPC are not supported. Ping between Amazon EC2 instances within VPC is supported as long as your operating system's firewalls, VPC security groups, and network ACLs permit such traffic.

10. Can You Monitor The Network Traffic In Your Vpc?

Yes. You can use the Amazon VPC Flow Logs feature to monitor the network traffic in your VPC.

11. Within Which Amazon Ec2 Region(s) Is Amazon Vpc Available?

Amazon VPC is currently available in multiple Availability Zones in all Amazon EC2 regions.

12. Can A Vpc Span Multiple Availability Zones?

Yes.

13. Can You Use Your Existing Amis In Amazon Vpc?

You can use AMIs in Amazon VPC that are registered within the same region as your VPC. For example, you can use AMIs registered in us-east-1 with a VPC in us-east-1.

14. How Do You Specify Which Availability Zone My Amazon Ec2 Instances Are Launched In?

When you launch an Amazon EC2 instance you must specify the subnet in which to launch the instance. The instance will be launched in the Availability Zone associated with the specified subnet.

15. Are There Any Bandwidth Limitations For Internet Gateways? Do You Need To Be Concerned About Its Availability? Can It Be A Single Point Of Failure?

No. An Internet gateway is horizontally-scaled, redundant, and highly available. It imposes no bandwidth constraints.

16. How Do You Secure Amazon Ec2 Instances Running Within My Vpc?

Amazon EC2 security groups can be used to help secure instances within an Amazon VPC. Security groups in a VPC enable you to specify both inbound and outbound network traffic that is allowed to or from each Amazon EC2 instance. Traffic which is not explicitly allowed to or from an instance is automatically denied.

In addition to security groups, network traffic entering and exiting each subnet can be allowed or denied via network Access Control Lists (ACLs).

17. What Are The Differences Between Security Groups In A Vpc And Network Acls In A Vpc?

Security groups in a VPC specify which traffic is allowed to or from an Amazon EC2 instance. Network ACLs operate at the subnet level and evaluate traffic entering and exiting a subnet. Network ACLs can be used to set both Allow and Deny rules. Network ACLs do not filter traffic between instances in the same subnet. In addition, network ACLs perform stateless filtering while security groups perform stateful filtering.

18. How Do You Determine Which Availability Zone My Subnets Are Located In?

When you create a subnet you must specify the Availability Zone in which to place the subnet. When using the VPC Wizard, you can select the subnet's Availability Zone in the wizard confirmation screen. When using the API or the CLI you can specify the Availability Zone for the subnet as you create the subnet. If you don’t specify an Availability Zone, the default "No Preference" option will be selected and the subnet will be created in an available Availability Zone in the region.

19. When You Call Describeinstances(), Do You See All Of My Amazon Ec2 Instances, Including Those In Ec2-classic And Ec2-vpc?

Yes. DescribeInstances() will return all running Amazon EC2 instances. You can differentiate EC2-Classic instances from EC2-VPC instances by an entry in the subnet field. If there is a subnet ID listed, the instance is within a VPC.

20. When You Call Describevolumes(), Do You See All of My Amazon EbS Volumes, Including Those In Ec2-classic And Ec2-vpc?

Yes. DescribeVolumes() will return all your EBS volumes.

21. Can You Employ Auto Scaling Within Amazon Vpc?

Yes

22. What Is The Ip Range Of A Default Vpc?

The default VPC CIDR is 172.31.0.0/16. Default subnets use /20 CIDRs within the default VPC CIDR.

23. How Many Default Vpcs Can You Have?

You can have one default VPC in each AWS region where your Supported Platforms attribute is set to "EC2-VPC".

24. How Many Default Subnets Are In A Default Vpc?

One default subnet is created for each Availability Zone in your default VPC.

25. Can You Launch Amazon Ec2 Cluster Instances In A Vpc?

Yes. Cluster instances are supported in Amazon VPC, however, not all instance types are available in all regions and Availability Zones.

26. What Is A Default Vpc?

A default VPC is a logically isolated virtual network in the AWS cloud that is automatically created for your AWS account the first time you provision Amazon EC2 resources. When you launch an instance without specifying a subnet-ID, your instance will be launched in your default VPC.

27. What Are The Advantage Of A Default Vpc?

When you launch resources in a default VPC, you can benefit from the advanced networking functionalities of Amazon VPC (EC2-VPC) with the ease of use of Amazon EC2 (EC2-Classic). You can enjoy features such as changing security group membership on the fly, security group egress filtering, multiple IP addresses, and multiple network interfaces without having to explicitly create a VPC and launch instances in the VPC.

28. What Accounts Are Enabled For Default Vpc?

If your AWS account was created after March 18, 2013 your account may be able to launch resources in a default VPC. See this Forum Announcement to determine which regions have been enabled for the default VPC feature set. Also, accounts created prior to the listed dates may utilize default VPCs in any default VPC enabled region in which you’ve not previously launched EC2 instances or provisioned Amazon Elastic Load Balancing, Amazon RDS, Amazon Elastic ache, or Amazon Redshift resources.

29. How Can You Know If My Account Is Configured To Use A Default Vpc?

The Amazon EC2 console indicates which platforms you can launch instances in for the selected region, and whether you have a default VPC in that region. Verify that the region you'll use is selected in the navigation bar. On the Amazon EC2 console dashboard, look for "Supported Platforms" under "Account Attributes". If there are two values, EC2-Classic and EC2-VPC, you can launch instances into either platform. If there is one value, EC2-VPC, you can launch instances only into EC2-VPC. Your default VPC ID will be listed under "Account Attributes" if your account is configured to use a default VPC. You can also use the EC2 DescribeAccountAttributes API or CLI to describe your supported platforms.

30. Can You Create Other Vpcs And Use Them In Addition To My Default Vpc?

Yes. To launch an instance into nondefault VPCs you must specify a subnet-ID during instance launch.

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