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AWS Certified Solutions Architect Exam Guide – Chapter-9

April 29, 2021 comments off

Understand what DNS is.
DNS is the methodology that computers use to convert human-friendly domain names (for example, amazon.com) into IP addresses (such as 192 .0.2.1).

Know how DNS registration works.

Domains are registered with domain registrars that in turn register the domain name with InterNIC, a service of ICANN. ICANN enforces uniqueness of domain names across the Internet. Each domain name becomes registered in a central database known as the WhoIS database. Domains are defined by their TLDs. TLDs are controlled by IANA in a root zone database, which is essentially a database of all available TLDs.

Remember the steps involved in DNS resolution.
Your browser asks the resolving DNS server what the IP address is for amazon.com. The resolving server does not know the address, so it asks a root server the same question. There are 13 root servers around the world, and these are managed by ICANN. The root server replies that it does not know the answer to this, but it can give an address to a TLD server that knows about .com domain names. The resolving server then contacts the TLD server. The TLD server does not know the address of the domain name either, but it does know the address of the resolving name server. The resolving server then queries the resolving name server. The resolving name server contains the authoritative records and sends these to the resolving server, which then saves these records locally so it does not have to perform these steps again in the near future. The resolving name server returns this information to the user’s web browser, which also caches the information.

Remember the different record types.

DNS consists of the following different record types: A (address record), AAAA (IPv6 address record), CNAME (canonical name record or alias), MX (mail exchange record), NS (name server record), PTR (pointer record), SOA (start of authority record), SPF (sender policy framework), SRV (service locator), and TXT (text record). You should know the differences among each record type.

Remember the different routing policies.

With Amazon Route 53, you can have different routing policies. The simple routing policy is most commonly used when you have single resource that performs a given function for your domain. Weighted routing is used when you want to route a percentage of your traffic to a particular resource of resources. Latency-based routing is used to route your traffic based on the lowest latency so that users get the fastest response times. Failover routing is used for DR and to route your traffic from a primary resource to a standby resource. Geolocation routing is used to route your traffic based on your end user’s location.


Exercises

In this section, you explore the different types of DNS routing policies that you can create using AWS. For specific step-by-step instructions, refer to the Amazon Route 53 information and documentation at http://aws.amazon.com/route53/. You will need your own domain name to complete this section, and you should be aware that Amazon Route 53 is not AWS Free Tier eligible. Hosting a zone on Amazon Route 53 should cost you a minimal amount per month per hosted zone, and additional charges will be levied depending on the routing policy you use. For current information on Amazon Route 53 pricing, refer to http://aws.amazon.com/route53/pricing/.

EXERCISE 9.1

Create a New Zone

  • Log in to the AWS Management Console.
  • Navigate to Amazon Route 53, and create a hosted zone.
  • Enter your domain name, and create your new zone file.
  • In the new zone file, you will see the SOA record and name servers. You will need to log in to your domain registrar’s website, and update the name servers with your AWS name servers.
  • After you update your name servers with your domain registrars, Amazon Route 53 will be configured to serve DNS requests for your domain.
    You have now created your first Amazon Route 53 zone.

EXERCISE 9.2
Create Two Web Servers in Two Different Regions
In this exercise, you will create two new Amazon EC2 web servers in different AWS regions. You will use these in the following exercises when setting up Amazon Route 53 to access the web servers.
Create an Amazon EC2 Instance

  • Log in to the AWS Management Console.
  • Change your region to Asia Pacific (Sydney).
  • In the Compute section, load the Amazon EC2 dashboard. Launch an instance, and select the first Amazon Linux Amazon Machine Image (AMI).
  • Select the Instance type, and configure your instance details. Take a close look at the different options available to you, and change your instance’s storage device settings as necessary.
  • Name the instance Sydney, and add a security group that allows HTTP.
  • Launch your new Amazon EC2 instance, and verify that it has launched properly.
    Connect to Your Amazon EC2 Instance
  • Navigate to the Amazon EC2 Instance in the AWS Management Console, and copy the public IP address to your clipboard.
  • Using a Secure Shell (SSH) client of your choice, connect to your Amazon EC2 instance using the public IP address, the user name ec2-user, and your private key.
  • When prompted about the authenticity 0f the host, type Yes, and continue.
  • You should now be connected to your Amazon EC2 instance. Elevate your privileges to root by typing #sudo su.
  • While you ’re logged’ In as the root user to your Amazon EC2 Instance, run the following command to install Apache httpd:

yum install httpd –y

  • After the installation has completed, run the command #service httpd start followed by #chkconfig httpd on.
  • Navigate to the EC2 instance, and type: cd /var/www/html
  • Type #nano index.html and press Enter.
  • In Nano, type This is the Sydney Server and then press Ctrl+X.
  • Type Y to confirm that you want to save the changes, and then press Enter.
  • Type #ls. You should now see your newly created index .html file.
  • In your browser, navigate to http: //yourpublicipaddress/index .html.
    You should now see your “This is the Sydney Server” home page. If you do not see this, check your security group to make sure you allowed access for port 80.

Create an Elastic Load Balancing Load Balancer

  • Return to the AWS Management Console, and navigate to the Amazon EC2 dashboard.
  • Create a load balancer named Sydney, leaving the Settings at their default values.
  • Create your security group, and allow all traffic in on port 80.
  • Configure health check, leaving the settings at their default values
  • Select your newly added instance. Add tags here if you want to tag your instances.
  • Click Create to provision your load balancer.

Create These Resources in a Second Region

  • Return to the AWS Management Console, and change your region to South America (Sao Paulo).
  • Repeat the three procedures in section to add a second Amazon EC2 instance and a load balancer in this new region.

You have now created two web servers in different regions of the world and placed these regions behind Elastic Load Balancing load balancers.
 
EXERCISE 9.3
Create an Alias A Record with a Simple Routing Policy

  1. Log in to the AWS Management Console, and navigate to the Amazon Route 53 dashboard.
  2. Select your newly-created zone domain name, and create a record set with the name A – Ipv4 Address
  3. Create an alias, leaving your routing policy set to Simple.
  4. In your web browser, navigate to your domain name. You should now see a welcome screen for the Sydney region. If you do not see this, check that your Amazon EC2 instance is attached to your load balancer and that the instance is in service. If the instance is not in service, this means that it is failing its health check. Check that Apache HTTP Server (HTTPD) is running and that your index.html document is accessible.
    You have now created your first Alias A record for the zone apex using the simple routing policy.

EXERCISE 9.4
Create a Weighted Routing Policy

  1. Return to the AWS Management Console, and navigate to the Amazon Route 53 dashboard.
  2. Navigate to hosted zones, and select your newly-created zone domain name.
  3. Create a record set with type set to developer. This will create a subdomain of developer. yourdomainname.com.
  4. Select your Sydney load balancer. Change the routing policy to Weighted with a value of 50 and a type of Sydney. Leave the other values at their default. Click Create. You will now see your newly-created DNS entry.
  5. Create another record set with type set to developer. This will add a new record with the same name you created earlier. Both records will work together.
  6. Select your Sao Paulo load balancer. Change the routing policy to Weighted with a value of 50 and type of Sao Paulo. Leave the other values at their defaults. Click Create. You will now see your newly-created DNS entry.
  7. Test your DNS by visiting http://developer.yourdomainname.com and refreshing the page. You should be accessing the Sydney server 50 percent of the time and the Sao Paulo server the other 50 percent of the time.
    You have now created a weighted DNS routing policy. You can continue to experiment with other routing policies by following the documentation at http://docs.aws.amazon.com/Route53/latest/DeveloperGuide/routing-routing-policy.html.
     
    EXERCISE 9.5
    Create a Hosted Zone for Amazon Virtual Private Cloud (Amazon VPC)
    Amazon VPC details are covered in Chapter4, “Amazon Virtual Private Cloud (Amazon VPC).”

Create a Private Hosted Zone

  1. Return to the AWS Management Console, and navigate to the Amazon Route 53 dashboard.
  2. Create a hosted zone, and enter your private domain name.
  3. Select the default Amazon VPC that you used in Exercise 9.2 to deploy the first server in this Asia Pacific (Sydney) region. Click Create. This will create a new zone file.
    Verify Amazon VPC Configuration
  4. Return to the AWS Management Console, and change your region to Asia Pacific (Sydney).
  5. In the Amazon VPC dashboard, choose your Amazon VPC.
  6. Click on the default Amazon VPC from the list. Ensure that both DNS resolution and DNS host names are enabled. These settings need to use private hosted zones.
    Create Resource Record Sets
  7. Return to the AWS Management Console, and navigate to the Amazon Route 53 dashboard.
  8. Select your newly-created private zone domain name, and create a record set.
  9. Enter the name you want to give to your Amazon EC2 instance (for example, Webserver1), and select Ipv4 address with no alias.
  10. Enter the internal IP address or your Amazon EC2 instance that you noted in
  11. Leave your routing policy set to Simple, and click Create
    Connect to Your Amazon EC2 Instance
  12. On the Amazon EC2 instances screen, wait until you see your virtual machine’s instance state as running. Copy the public IP address to your clipboard.
  13. Using an SSH client of your choice, connect to your Amazon EC2 instance using the public IP address, the user name ec2-user, and your private key. For example, if you’re using Terminal in OSX, you would type the following command:
    ssh ec2-user@publicipaddresshere –i MyPrivateKey.pem
  14. When prompted about the authenticity of the host, type Yes and continue. You should now be connected to your Amazon EC2 instance.
     
  15. While you’re logged in to your Amazon EC2 instance, run the following command to check If the host names in Amazon Route 53 are resolving:
    nslookup webserver1.yourprivatehostedzone.com
  16. You should receive a non-authoritative answer with the host name and IP address for the record set that you created in Amazon Route 53.
    You have now created a private hosted zone in Amazon Route 53 and associated it with an Amazon VPC. You can continue to add instances in Amazon VPC and create resource record sets for them in Amazon Route 53. These new instances would be able to intercommunicate with the instances in the same Amazon VPC using the domain name that you created.
    Remember to delete your Amazon EC2 instances and Elastic Load Balancing load balancers after you’ve finished experimenting with your different routing policies. You may also want to delete the zone if you are no longer using it.
     
    Review Questions
    Which type of record is commonly used to route traffic to an IPv6 address?
  • An A record
  • A CNAME
  • An AAAA record
  • An MX record

Where do you register a domain name?

  • With your local government authority
  • With a domain registrar
  • With InterNIC directly
  • With the Internet Assigned Numbers Authority (IANA)

You have an application that for legal reasons must be hosted in the United States when U.S. citizens access it. The application must be hosted in the European Union when citizens of the EU access it. For all other citizens of the world, the application must-be hosted in Sydney. Which routing policy should you choose in order to achieve this?

  • Latency-based routing
  • Simple routing
  • Geolocation routing
  • Failover routing

Winch type of DNS record should you use to resolve an IP address to a domain name?

  • An A record
  • A C Name
  • An SPF record
  • A PTR record

You host a web application across multiple AWS regions in the world, and you need to configure your DNS so that your end users will get the fastest network performance possible. Which routing policy should you apply?

  • Geolocation routing
  • Latency-based routing
  • Simple routing
  • Weighted routing

Which DNS record should you use to configure the transmission of email to your intended mail server?

  • SPF records
  • A records
  • MX records
  • SOA record

Which DNS records are commonly used to stop email spoofing and spam?

  • MX records
  • SPF records
  • A records
  • C names

You are rolling out A and B test versions of a web application to see which version results in the most sales. You need 10 percent of your traffic to go to version A, 10 percent to go to version B, and the rest to go to your current production version. Which routing policy should you choose to achieve this?

  • Simple routing
  • Weighted routing
  • Geolocation routing
  • Failover routing

Which DNS record must all zones have by default?

  • SAF
  • TXT
  • MX
  • SOA

Your company has its primary production site in Western Europe and its DR site in the Asia Pacific. You need to configure DNS so that if your primary site becomes unavailable, you can fail DNS over to the secondary site. Which DNS routing policy would best achieve this?

  • Weighted routing
  • Geolocation routing
  • Simple routing
  • Failover routing

Which type of DNS record should you use to resolve a domain name to another domain name?

  • An A record
  • A CNAME record
  • An SPF record
  • A PTR record

Which is a function that Amazon Route 53 does not perform?

  • Domain registration
  • DNS service
  • Load balancing
  • Health checks
     
    Which DNS record can be used to store human-readable information about a server, network and other accounting data with a host?
  • A TXT record
  • An MX record
  • An SPF record
  • A PTR record

Which resource record set would not be allowed for the hosted zone example.com?

  • www.example.com
  • www.aws.example.com
  • www.example.ca
  • www.beta.example.com

Which port number is used to serve requests by DNS?

  • 22
  • 53
  • 161
  • 389

Which protocol is primarily used by DNS to serve requests?

  • Transmission Control Protocol (TCP)
  • Hyper Text Transfer Protocol (HTTP)
  • File Transfer Protocol (FTP)
  • User Datagram Protocol (UDP)

Which protocol is used by DNS when response data size exceeds 512 bytes?

  • Transmission Control Protocol (TCP)
  • Hyper Text Transfer Protocol (HTTP)
  • File Transfer Protocol (FTP)
  • User Datagram Protocol (UDP)

What are the different hosted zones that can be created in Amazon Route 53?

  • Public hosted zone
  • Global hosted zone
  • Private hosted zone
    A. 1 and 2
    B. 1 and 3
    C. 2 and 3
    D. 1, 2, and 3
     
    Amazon Route 53 cannot route queries to which AWS resource?
  • Amazon CloudFront distribution
  • Elastic Load Balancing load balancer
  • Amazon EC2
  • AWS OpsWorks

When configuring Amazon Route 53 as your DNS service for an existing domain, which is the first step that needs to be performed?

  • Create hosted zones.
  • Create resource record sets.
  • Register a domain with Amazon Route 53.
  • Transfer domain registration from current registrar to Amazon Route 53.
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