Route 53 Global DNS Flashcards
R53 Hosted Zone
DNS Data base for a domain
what the DNS system references Authoritative for a domain
What is the resiliency of R53 ?
it’s Globally resilient with multiple DNS servers
What does Host Zones contain ?
Host DNS records
e.g. A, AAAA, MX NS and TXT
How many name servers are there per hosted zone ?
4 R53 name servers(NS) specific for the zone
accessible from public internet and VPC
Private Hosted Zones
associated with VPC
only accessible in those VPCs
Split View or Split Horizon DNS
overlapping public and private for public and internal uses with the same Zone name
Route 53 Health Checks
health checks are separate from, but are used by records
checks if an record is healthy or unhealthy
in most cases an unhealthy record is not returned in queries
Some benefits of R53 health checks
endpoint, cloudWatch alarms, check of checks calculated
How often are checks by default
check every 30s (every 10s cost extra)
checks connection by TCP, HTTP/HTTPs with string matching
A records
maps a Name to an Ip address
Limitation of Cnames
CNAME is invalid for naked/Apex domain
i.e. catagram.io
Alias Record
maps a name to an AWS resource
can be used for both naked/apex and normal
no charge for Alias pointing at AWS resources
Why user an Alias record over a CName record
Many AWS services us a DNS name (ELB)
Name : catatgram.io ==> ELB would be invalid
for AWS services the default is an Alias
Route53 Simple Routing
simple routing doesn’t support health checks - all values are returned for a record when queried
What case would simple routing be best ?
use simple routing when you want to route requests towards one service such as a web server
Route53 Weighted Routing
Each record is return based on it’s record weight vs total weight
if a chosen record is unhealthy, the process of selection is repeated until a healthy record is chosen
What does it mean when a record has a ‘0’ in Weighted Routing ?
A ‘0’ weight means a record is never returned unless all are ‘0’ then all are considered
Route53 Failover Routing
if the target of the health check is ‘Healthy’ the primary record is used
if the target of the health check is unhealthy any queries return the secondary record of the same name
When would you user weighted Routed ?
simple load balancing or testing new software versions
What is the user case for Failover Routing ?
user when you want to configure active passive failover
a common architecture is to use failover for a ‘out of band’ failure / maintenance page for a service (e.g EC2/S3 )
Route53 Multi Value Routing
Muli Value Routing supports Multiple records with the same name
Up to 8 ‘healthy ’ records are returned. if more exit 8 are randomly selected
each record has it’s own health check if a not healthy the record won’t be returned
When would you user multi value routing ?
Multi value routing improves the availability
it is not a replacement for load balancing
Route53 Latency-Based Routing
AWS maintains a database of latency between the users general location and the regions tagged in records
Latency-based Routing supports one record with the same name in each AWS region
The record returned is the one which offers the lowest estimated latency and is healthy
