This document provides an overview of Amazon Route 53 DNS services including: - IPv4 and IPv6 address spaces and how Route 53 resolves domain names to IP addresses using A records. - Common DNS record types like NS, SOA, CNAME and how they work. - Route 53 routing policies for controlling traffic like simple, weighted, latency, failover and geolocation routing. - How alias records can simplify configuration by automatically reflecting changes to referenced resources. - A example of setting up Route 53 with domains, record sets, Elastic Load Balancers and instances across regions.

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2. Amazon Web Services
Route53: DNS service

3. Route53 :DNS background: IPV4 VS IPV6
• The IPv4 space is a 32 bit field and has over 4 billion different addresses
(4,294,967,296 to be precise).
Class A,B,C
0.0.0.0 – 255.255.255.255 256X256x256x256
10.0.1.0/24
• IPv6 was created to solve this depletion issue and has an address space of 128bits
which in theory is 340,282,366,920,938,463,463,374,607,431,768,211,456 addresses or
340 undecillion addresses.

4. Route53 :DNS Background: SOA Record
The SOA record stores information about:
- The name of the server that supplied the data.
- The administrator.
- The current version of the data file.
- The number of seconds a secondary name server should wait before checking
for updates.
- The number of seconds a secondary name server should wait before retrying a
failed zone transfer.
- The maximum number of seconds that a secondary name server can use data
before it must either be refreshed or expire.
- The default number of seconds for the time—to-live file on resource records.

5. Route53 :DNS Background
NS Records:
NS stands for Name Server records and are used by Top Level Domain servers to direct traffic to the
Content DNS server which contains the authoritative DNS records.
A Records:
An "A“ record is the fundamental type of DNS record and the "A" in A record stands for
"Address". The A record is used by a computer to translate the name of the domain to
the IP address. For example http://www.zekelabs.com might point to http://123.10.10.80.
TTL:
The length that a DNS record is cached on either the Resolving Server or the users
own local PC is equal to the value of the "Time To Live" (TTL) in seconds. The lower
the time to live, the faster changes to DNS records take to propagate throughout the
internet.

6. Route53 :Other Records
CNames Records:
A Canonical Name (CName) can be used to resolve one domain name to another. For
example, you may have a mobile website with the domain name http://m.google.com that
is used for when users browse to your domain name on their mobile devices. You may
also want the name http://mobile.google.com to resolve to this same address.
Alias Records:
Alias records are used to map resource record sets in your hosted zone to Elastic Load
Balancers, C|oudFront distributions, or S3 buckets that are configured as websites.
Alias records work like a CNAME record in that you can map one DNS name
(example.com) to another ‘target’ DNS name 172.31.45.0 (elb1234.elb.amazonaws.com).
Key difference - A CNAME can't be used for naked domain names (zone apex). It must
be either an A record or an Alias.

7. Route53 :Alias Record
• Alias resource record sets can save you time because Amazon Route-53 automatically
recognizes changes in the record sets that the alias resource record set refers to.
• For example, suppose an alias resource record set for zekelabs.com points to an ELB
load balancer at elb1-1234.us-east.elb.amazonaws.com.
If the IP address of the load balancer changes, Amazon Route 53 will automatically reflect
those changes in DNS answers for example.com without any changes to the hosted zone
that contains resource record sets for example.com.

8. Route53: Routing Policy
Routing Policy Types:
- Simple
- Weighted
- Latency
- Failover
- Geolocation

9. Route53: Routing Policy Types
Simple Routing Policy
This is the default routing policy when you create a new record set. This is most commonly
used when you have a single resource that performs a given function for your domain.
For example, one web server that serves content for the http://zekelabs.com website.

10. Route53: Simple Routing Policy

11. Route53: Routing Policy Types: Weighted Routing Policy:
Allows you to split your traffic based on different weights assigned.
e.g. you can assign 10% of your traffic to one AZ and 90% to the other AZ.
Does this over the length of the day

12. Route53: Routing Policy Types : Weighted Routing Policy

13. Route53: Routing Policy Types: Failover Routing Policy:
• This is equivalent to the high availability concept. Make one ELB on active mode and
the other on standby mode. Switch will happen automatically on failover.
• We have to create health check status
- one to check health of ELB, other on the whole site
• Create record sets to attach to the ELBs
Make one ELB as primary and other as secondary

14. Route53: Failover Routing Policy

15. Route53: Latency Routing Policy
Latency based routing allows you to route your traffic based on the lowest network latency for
your end user (ie which region will give them the fastest response time).
To use latency—based routing you create a latency resource record set for the Amazon EC2 (or
ELB) resource in each region that hosts your website. When Amazon Route 53 receives a query
for your site, it selects the latency resource record set for the region that gives the user the lowest
latency. Route 53 then responds with the value associated with that resource record set.

16. Route53: Latency Routing Policy

17. Route53: Routing Policy Types: GeoLocation Routing Policy
•User is redirected based on the region of the DNS request.
•This can be configured using record sets.

18. Route53: Geolocation Routing Policy

19. More about Route 53:LAB
- Purchasing domain name (or just use a dummy domain name)
- Go to Hosted zone and create record sets
- Create diff record set and different routing policies. (These are A records)
- Select a region closest you
- launch 1 ELB and 2 instances (with webservers running on it)
- Check both webservers are runnning through ELB
- Go to farthest region (sydney) and create an instance wih webserver (with SSh and http) and create
a sydney ELB
- Check if webserver is working fine
Get step by step approach to migrate from existing DNS to Route53 go to this link:
http://docs.aws.amazon.com/Route53/latest/DeveloperGuide/MigratingDNS.html
.

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