Route 53

Question 1

Route 53

Answer 1

• authoritative DNS - customer (you) can update DNS records
• domain registrar
• health checks
• 100% availability SLA

Question 2

TLD

Answer 2

top level domain (.com, .gov)

Question 3

SLD

Answer 3

second level domain - amazon.com

Question 4

How does DNS work?

Answer 4

Question 5

How does DNS work?

Answer 5

Question 6

DNS record types

Answer 6

• A - address
• AAAA - A record for IPv6
• CNAME - maps hostname to a hostname
  
  • can’t create a CNAME record for top node of DNS namespace
    
    • i.e. example.com cname record not allowed but www.example.com is ok
  • Alias - map hostname to aws resource
    
    • works for BOTH root and non-root domain
    • free of charge
    • cannot set TTL
    • always an A record
    • CANNOT alias an EC2 DNS name
• NS - name server for the hosted zone

Question 7

DNS TTL

Answer 7

• cached at DNS resolvers
  
  • high ttl - less traffic on route53, possibly outdated record on client
  • low ttl - more traffic on route53, easy to change records
  • except for alias records, TTL is mandatory for each DNS record

Question 8

DNS hosted zones

Answer 8

• public - contains records that specify how to route traffic on internet
• private - only within VPC can names be resolved

Question 9

Simple routing policy

Answer 9

• typically, route traffic to a single resource
• can specify multiple values in same record returned to client. client will randomly choose one
• when alias enabled, specify only ONE aws resource
• no health checks

Question 10

weighted routing policy

Answer 10

• control % of requests go to a specific resource based on weights
• weights don’t add to 100. just a percentage of sum of all weights
  
  • 0 value for all weights? - all records will be chosen equally
• can do health cases
• use case: load balancing

Question 11

failover routing policy

Answer 11

switch dns record to point to a separate instance when health check fails

Question 12

latency based routing policy

Answer 12

• redirect to resource that has least latency
  
  • based on traffic between users and aws regions
  • supports health checks (has failover capability)

Question 13

geolocation based routing policy

Answer 13

• different than latency based! us toe users actual location
• health check support

Question 14

geoproximity based routing policy

Answer 14

• ability to shift more traffic to resources based on a defined bias
• to change size of geographic region, specify bias values
  
  • higher bias = more traffic to resource
  • lower bias = less traffic to resource
• must use (advanced) traffic flow feature

Question 15

multi-value based routing policy

Answer 15

• route 53 returns multiple values/resources
• up to 8 healthy records for each multi-value query
• NOT a substitute for having an ELB
  
  • multi-value is ‘client-side’ load balancing
• health check support

Question 16

R53 health checks

Answer 16

• usually used for public resources
  
  • route 53 public health checkers live outside your vpc and cannot access private endpints
  • for private resources, reate a cloudwatch metric and associate the alarm, then create a health check that checks the alarm itself
• used for automated DNS failover
• calculated health check - monitors other health checks
• integrated with CloudWatch