EC2

Question 1

EC2 Enhanced Networking

Answer 1

Uses advanced virtualisation (Single Route - IO Virtualisation) to deliver:

• Higher I/O
• Lower host CPU usage
• More bandwidth
• Higher packets per second (PPS)
• Consistent lower latency

Available for no charge on most EC2 types.

Question 2

How many hosts does a EC2 instance run in?

Answer 2

ONE AZ. If a AZ faces major issue, it will impact EC2 instances. (No HA by default).

Question 3

EC2 Charges at Stopped State

Answer 3

Still incur charges for EBS

Question 4

Permission error when SSH into Linux instance. How do I fix it?

Answer 4

Key is missing permissions. Need to perform chmod 0400 command on the .pem key.

Question 5

EC2 Status Checks

Answer 5

1. System Status Checks: makes sure traffic can reach the hardware. Checks for loss of power, network connectivity, software and hardware issues.
2. Instance Status Checks: makes sure instance OS is available and accepting traffic. Checks for corrupted file system, incorrect instance networking, and/or OS kernel issues.

Question 6

Elastic IP’s

Answer 6

• Static IPv4 address
• can only attach to one instance at a time
• can mask a system/instance failure, by remapping to another working instance
• Max 5 EIP’s

Question 7

User Data Key Limitations

Answer 7

• Opaque to EC2 instance, just a block of data
• NOT secure. Don’t use it for passwords
• Limited to 16KB in size
• Can be modified when instance stopped
• ONLY executed at launch
• Accessed via metadata IP: 169.254.169.254/latest/user-data

Question 8

Cloudformation::init (cfn-init)

Answer 8

Used to maintain desired state of EC2 instance through a helper script. Can control packages, groups, users, sources, files, commands, and services.

Question 9

Scheduled reserved instances

Answer 9

• Launch within time window you reserve

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Question 10

EC2 Status Checks Auto Recovery

Answer 10

Can create a CloudWatch alarm and auto recovery, which will try to fix the issue, including, moving to a new host (if required).

Question 11

Types of spot requests

Answer 11

1. One-time request: will launch instance if spot request is fulfilled.
2. Persistent: will stay in queue as valid until request is value.

Question 12

AMI regional/AZ?

Answer 12

AMI ID’s differ across regions

Question 13

Dedicated Hosts limitation

Answer 13

1. AMI Limits: No RHEL, SUSE Linux, and Windows AMIs are NOT supported.
2. Amazon RDS instances are not supported
3. Placement groups are NOT supported

Question 14

Elastic Network Interfaces

Answer 14

• Secondary ENI + MAC is used for transfering licenses between multiple instances
• Multi homed (subnets) management can give multiple connections
• Different Security Groups
• OS: doesnt see public IPv4 address.
• Bound to specific AZ

Question 15

Security Groups

Answer 15

Can reference other Security Groups (instead of IP).