AWS Certified SysOps Administrator - Associate Questions and Answers (Dumps and Practice Questions)

Question : You have identified network throughput as a bottleneck on your m.small EC instance when
uploading data Into Amazon S3 In the same region. How do you remedy this situation?

1. Add an additional ENI
2. Change to a larger Instance
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4. Use EBS PIOPS on the local volume

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Explanation: https://media.amazonwebservices.com/AWS_Amazon_EMR_Best_Practices.pdf
Because the instance size determines the amount of network bandwidth assigned to the instance.

Question : Your application currently leverages AWS Auto Scaling to grow and shrink as load Increases/ decreases and has been performing well. Your marketing team expects
a steady ramp up in traffic to follow an upcoming campaign that will result in a 20x growth in traffic over 4 weeks. Your forecast for the approximate number of Amazon EC2
instances necessary to meet the peak demand is 175. What should you do to avoid potential service disruptions during the ramp up in traffic?

1. Ensure that you have pre-allocated 175 Elastic IP addresses so that each server will be able to obtain one as it launches
2. Check the service limits in Trusted Advisor and adjust as necessary so the forecasted count remains within limits.
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4. Pre-warm your Elastic Load Balancer to match the requests per second anticipated during peak demand prior to the marketing campaign

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Explanation: Expecting a spike in traffic? While AWS ELB's are designed to handle large (20k/sec) loads when the level reached this gradually (several hours), it struggles when traffic
spikes this high in shorter periods (several minutes). If you're expecting the latter, simply call Amazon Web Services support team and request that they pre warm it to make the
increase gradual and facilitate the ELB. No Large, Sudden Spikes : This is a well-known one, but may still surprise some people, ELB has not been designed to stand large/sudden
spikes of traffic. It may seem counter-intuitive (and in fact it is for me) that a service designed for scalability has this limitation, but it is a hard fact.
In AWS words: I noted your primary question is if ELB imposes a restriction on data/seconds. This is not the case and in fact the only real limiting factor of ELB includes large
sudden spikes, as ELB is designed to scale due to load spread over a period of time. Large sudden spikes generally require pre-warms.
Given this I think explaining how ELB distributes traffic would provide some clarification. ELB uses a least number of waiting connections algorithm, once the request reaches the ELB
node in the AZ. At the AZ level traffic is distributed using DNS in a round robin fashion.
Interesting. Please note the "pre-warm" concept. So when you expect a large/sudden spike of traffic, you just get on the phone with AWS folks and tell them to pre-warm your ELB and
problem solved! just a small caveat here, you may not actually know when the large/sudden spike of traffic will come ... anyway, let's see what AWS have to say when asked about what
a large sudden spike is and about this pre-warming thing:
"Large sudden spikes" means the sudden increase in the number of request to the ELB.Indeed this happens when you are load testing with a tool which sends large number of request to
the ELB in a particular period.
Since you have sent large number of request as part of your load test, the ELB sent an error response as it was not able to handle the sudden increase in the incoming request.
About this issue : This is a common issue most of our customer face during load test without pre-warming the ELB.
What is Prewarming?
Configuring the load balancer to have the appropriate level of capacity based on the traffic that you expect.
For pre-warming,We get the following details from the customer.
1) Start and end dates of your tests or expected flash traffic,
2) Expected request rate per second
3) Total size of the typical request/response that you will be testing.

Now, we could have a Large/sudden Spike during a load test OR i.e. if a plane crashes and everyone rushes to our customers website (news outlet) to read the news. Pre-warming seems
not an option here.

So we definitely wanted to understand how a Large/sudden Spike is exactly defined, so we just asked again. AWS answer:
> "Large Spike", what does it mean, are we talking about users request being increased from let say 200 to 2000?
Honestly, I don't think there are clear cut numbers we can provide, however, an initial ELB size can handle probably a request count average of say 100 or so per second(these are my
own best guesses, not official values). If you anticipate to have more than say 300 requests/second on a go, you may need the pre-warm that my colleagues talked about earlier to have
the ELB initial size bumped up.
>> or how does it calculate and what would be considered as large spike ?
The design of the ELB is that there is a threshold beyond which the ELB scales up. For example if you create an ELB now it will be at its minimal size and once traffic starts flowing
through it will scale up as traffic increases and at each ELB magnitude there is a defined threshold value. If the requests have surpassed the threshold value in a sudden
behavior(spike) there will be a problem as the ELB scales gradually. You may be interested in the actual value of the thresholds and unfortunately I do not have the exact values.
When an ELB scales from one level to another there is need to give underlying host a few minutes to reconfigure. To ensure that there is no outage during this scale up period we
recommend the multi-AZ set up.

Question : When attached to an Amazon VPC which two components provide connectivity with external networks? Choose answers
A. Elastic IPS (EIP)
B. NAT Gateway (NAT)
C. Internet Gateway {IGW)
D. Virtual Private Gateway (VGW)

1. A,D
2. B,D
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4. C,D

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Explanation: So question is talking about inbound as well as outbound traffic.

VGW : Virtual private gateway. By default, instances that you launch into a virtual private cloud (VPC) can't communicate with your own network. You can enable access to your network
from your VPC by attaching a virtual private gateway to the VPC, creating a custom route table, and updating your security group rules.
The Amazon side of a VPN connection that maintains connectivity. The internal interfaces of the virtual private gateway connect to your VPC via the VPN attachment and the external
interfaces connect to the VPN connection, which leads to the customer gateway.

Internet gateway : Connects a network to the Internet. You can route traffic for IP addresses outside your VPC to the Internet gateway.
An Internet gateway is a horizontally scaled, redundant, and highly available VPC component that allows communication between instances in your VPC and the Internet. It therefore
imposes no availability risks or bandwidth constraints on your network traffic. An Internet gateway serves two purposes: to provide a target in your VPC route tables for
Internet-routable traffic, and to perform network address translation (NAT) for instances that have been assigned public IP addresses.

Elastic IP address : A fixed (static) IP address that you have allocated in Amazon EC2 or Amazon VPC and then attached to an instance. Elastic IP addresses are associated with your
account, not a specific instance. They are elastic because you can easily allocate, attach, detach, and free them as your needs change. Unlike traditional static IP addresses,
Elastic IP addresses allow you to mask instance or Availability Zone failures by rapidly remapping your public IP addresses to another instance.
We assign each instance in a nondefault VPC only a private IP address, unless you specifically request a public IP address during launch, or you modify the subnet's public IP address
attribute. To ensure that an instance in a nondefault VPC that has not been assigned a public IP address can communicate with the Internet, you must allocate an Elastic IP address
for use with a VPC, and then associate that EIP with the elastic network interface (ENI) attached to the instance.
When you associate an EIP with an instance in a default VPC, or an instance in which you assigned a public IP to the eth0 network interface during launch, its current public IP
address is released to the EC2-VPC public IP address pool. If you disassociate an EIP from the instance, the instance is automatically assigned a new public IP address within a few
minutes. However, if you have attached a second network interface to the instance, the instance is not automatically assigned a new public IP address; you'll have to associate an EIP
with it manually.
NAT instance : An instance that is configured to perform NAT in a VPC. A NAT instance enables private instances in the VPC to initiate Internet-bound traffic without being directly
reachable from the Internet. Instances that you launch into a private subnet in a virtual private cloud (VPC) can't communicate with the Internet. You can optionally use a network
address translation (NAT) instance in a public subnet in your VPC to enable instances in the private subnet to initiate outbound traffic to the Internet, but prevent the instances
from receiving inbound traffic initiated by someone on the Internet.

Instances in a VPC only have access to the public internet if they have an Elastic IP or if their subnet is routed through a NAT instance. Assign an Elastic IP (if you like, you can
have this done automatically on launch so you don't have to worry about associating/deassociating) and it'll have access.

"when attached" to a VPC is the key words. You can only deploy IGW and VGW from the VPC area of the console. EIPs and NATs aren't "attached" to the VPC,
they are EC2 specific. On question one the EIP alone doesn't provide routing from instances to external networks, you have to have either an IGW or VGW.
If you remove both IGWs and VGWs from a VPC then instances on that VPC won't be able to access anything outside the VPC, regardless of whether an EIP is present or not
A NAT instance that allows instances in a private subnet to access the internet still uses the IGW attached to the VPC in order to provide that internet access as it will
reside in a public subnet. Elastic IPs would be attache

Its C and D. IGW for internet and VGW for external network (corp). A NAT won't get you out to the internet without IGW.

AWS Certified SysOps Administrator - Associate Questions and Answers (Dumps and Practice Questions)

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