Route 53 (associate)

Question 1

What is DNS?

Answer 1

• It’s a Domain Name system which translate the human friendly host names into the machine IP addresses & is the backbone of the internet
• DNS uses hierarchical naming structure:
  1. .com
  2. example.com
  3. www.example.com

Question 2

What are the different DNS Terminologies?

Answer 2

1. Domain registrar: Amazon route 53, godaddy, etc
2. DNS record: A, AAAA, CNAME. NS…
3. Zone file: contains DNS records
4. Name server: resolved DNS queries (authoritative or non-authoritative)
5. Top level domain (TLD): .com, .us, .in, .gov, .org
6. Second level domain (SLD): Amazon.com, google.com

https://api.www.example.com.
(. at the end is the root)
(. after example and everything with it is the TLD)
(. After www and everything after is the SLD)
(. After api and everything after is sub domain)
(api and everything after is the FQDN (fully qualified domain name)
(http is the protocol)
And the whole thing is called the URL

Question 3

__________ is a highly availabl, scalable, fully managed & authoritative DNS which means the customer can update the DNS record

Answer 3

Amazon Route 53

Question 4

The route 53 records will contain what?

Answer 4

• Domain/subdomain name (ex. Example.com)
• Record type (ex. A or AAAA)
• Value (12.34.56.78)
• Routing Policy (how route 53 responds to queries)
• TTL(amount of time the record cached at DNS resolvers)

Question 5

What are the different route 53 record types?

Answer 5

• A: maps a host name to IPv4
• AAA: maps a host name to IPv6
• CNAME: maps a host name to another host name (the target is a domain name that must have an A or AAA record & can’t create CNAME record for the top node of a DNS namespace)(ex. Can create one for example.com but can create one for www.example.com)
• NS: name servers for the hosted zone (control how traffic is routed for a domain)

Question 6

____________ is a container for record that define how to route traffic to a domain and it’s subdomains

Answer 6

Route 53 - Hosted Zones

Question 7

What are the two types of hosted zones?

Answer 7

1. Public hosted zones: contains record that specify how to route traffic on the internet (public domain name)
2. Private hosted zones: contain record that specify how you route traffic within one or more VPC

• Pay 0.50 per month per hosted zone (not free)

Question 8

_________ means time to live, how a client has to cache results

Answer 8

Route 53 Record TTL

1. High TTL (ex 24hrs)
   - less traffic on route 53 & possibly outdated record
2. Low TTL (ex 60secs)
   - More traffic on Route 53
   - Record are outdated less time and easy to change records

• The TTL is mandatory for every DNS record except for Alias Record

Question 9

What is the difference between CNAME & Alias ?

Answer 9

CNAME:
- Points a host name to any other host name ( app.mydomain.com => Blabla.anything.I’m)
- Only for non root domain (aka.something.mydomain.com)

Alias:
- Points a host name to an AWS resource (app.mydomain.com=> Blabla.Amazonas.com)
- Works for root domain & non root domain (aka.mydomain.com)
- Free of charge
- Native health check
- Maps to a host name to an AWS resource
- An extension to DNS functionality
- Can be used for the top node of a DNS namespace
- Alias record is always of type A/AAAA for AWS resources (IPv4 / IPv6)
- Can’t set the TTL (set automatically by route 53)

Question 10

What are the targets for Alias records?

Answer 10

• ELB
• Cloudfront distributions
  -API Gateway
• Elastic beanstalks environments
• S3 websites
• VPC interface endpoints
• Global accelerator accelerator
• Route 53 record in the same hosted zone
• You can’t set an ALIAS record for an EC2 DNS name

Question 11

_________ define how route 53 responds to DNS queries

Answer 11

Route 53 routing policy

Question 12

What are the different routing policies for route 53?

Answer 12

1. Simple
2. Weighted
3. Failover
4. Latency based
5. Geolocation
6. Multi- Value answer
7. Geoproximity

Question 13

What are some features of simple routine policy?

Answer 13

1. Typically route traffic to a single resource
2. Can specify multiple values in the same record
3. If multiple values are returned, a random one is chosen by the client
4. When Alia’s enabled, specify only one AWS resource
5. Can’t be associated with health checks

Question 14

What are some features of weighted routine policy?

Answer 14

1. Control the % of the request that go to each specific resource
2. Assign each record a relative weight:
   - Traffic (%) = weight for a specific record/ sum of all the weights for all records
3. DNS records must have the same name & type
4. Can be associated with health checks
5. Use cases: load balancing, between regions, testing new applications versions
6. Assign a weight of 0 to a record to stop spending traffic to a resource
7. If all record have weight of 0, then, all record will be returned equally

Question 15

What are some features of latency -based routine policy?

Answer 15

1. Redirects to the resource that has the least latency is to us
2. Super helpful when latency for users is priority
3. Latency is based on traffic between users & AWS regions
4. Germany user may be directed to the US (if that’s the lowest latency)
5. Can be associated with health checks (has failover capability)

Question 16

What are some features in route 53 health checks?

Answer 16

1. HTTP health checks are only for public resources
2. Health check leads to automated DNS failover
3. Health checks are integrated with CW metrics

Question 17

What re the 3 different types of health checks ?

Answer 17

1. Health checks that monitor an endpoint (application, server, other AWS resource)
2. Health checks that monitor other health checks (calculated health checks)
3. Health checks that monitor cloudwatch alarms (full control) throttles of dynamoDB, alarms on RDS, Custom metrics

Question 18

Describe how health checks monitor an Endpoint

Answer 18

1. About 15 global health checkers will check the endpoint health
   - Heathy/unhealthy threshold -3 default
   - Interval - 30sec (can set to 10 sec higher cost)
   - Supported protocol: HTTP, HTTPS & TCP
   - If > 18% of health checkers report the endpoint is healthy route 53 considers it health ither its unhealthy
   - Ability to choose which locations you want route 53 to use
2. Health checks pass only when the endpoint responds with the 2xx and 3xx codes
3. Health checks can be setup to pass/fail based on the text in the first 5120 bytes of the response
4. Configure you router/firewall to allow incoming request from route 53 health checkers

Question 19

What are some features of calcite’s health checks for route 53?

Answer 19

1. Combine the results of multiple health check into a single health check
2. You can use OR, And, or NOT
3. Can monitor up to 256 child health checks
4. Specify how many of the health checks need to pass to make the parent pass
5. Usage: perform maintenance to your website without causing all health checks to fail

Question 20

How do you make a health check on a private hosted zones?

Answer 20

• Route 53 health checkers are outside the VPC
• They can’t access private endpoints (private VPC or on premises resources)
• You can create a cloudwatch metric and associate a cloudwatch alarm, then, create a health check that checks the alarm itself

Question 21

What are some features of geolocation routing policy ?

Answer 21

1. Different from latency based
2. This routing is based on user location
3. Specify location by continent, country or by US state (if there’s overlapping most precise location selected)
4. Should create a “default” record (in case there’s no match on location)
5. Use cases: website localization, restrict content distribution, load balancing
6. Can be associated with health checks

Question 22

What are some features of geoproximity routing policy?

Answer 22

1. Route traffic to your resources based on the geographic location of users & resources
2. Ability to shift more traffic to resources based on the defined bias
3. To change the size of the geographic region, specify bias values:
   - To expand (1 to 99): more traffic to the resource
   - To shrink( -1 to 99) less traffic to the resource
4. Resources can be:
   - AWS resource (specify AWS region)
   - Non- AWS resources (specify latitude & longitude)
5. You must use route 53 traffic flow (advance) to use this feature

Question 23

The _______________ is really helpful when you need to shift traffic from one region to another by increasing the bias

Answer 23

Geoproximity routing policy

Question 24

What are some features of the IP-based routing policy?

Answer 24

• Routing is based on clients’ IO addresses
• You provide a list of CIDRs for your clients & the corresponding endpoints/locations (users - IP to endpoint mapping)
• Used cases: optimizes performance, reduce network costs
• Example: Route end users from a particular ISP to a specific endpoint

Question 25

What are some features of Multi-Value routing policies?

Answer 25

1. Use when routing traffic to multiple resources
2. Rouge 53 return multiple values/resources
3. Can be associated with health checks (return only values for healthy resources)
4. Up to 8 healthly record are returned for each multi-value query
5. Multi- Value is not a substitute for having an ELB

Question 26

What is the difference between domain registrar & DNS service?

Answer 26

• You but or registrar your domain name with a domain registrar typically by paying annual charges (like godaddy, Amazon registrar, etc)
• The domain registrar usually provided you with a DNS service to manage your DNS records but you use another DNS service to manage your DNS records

Question 27

Describe how to use a 3rd party registrar with Amazon Route 53

Answer 27

• If you buy your domain on a 3rd party register you can still use route 53 S the DNS service provider

1. Create a hosted zone in route 53
2. Update NS records on 3rd party website to use route 53 name servers

• Domain registrar = DNS service
• But every domain registrar usually comes with some DNS features