Route53 Routing Policies

Question 1

What are the Route53 Routing Policies in AWS?

Answer 1

• Simple Routing
• Weighted Routing
• Latency-based Routing
• Failover Routing
• Geolocation Routing
• Geoproximity Routing (Traffic Flow Only)
• Multivalue Answer Routing

Question 2

How does Amazon’s Simple Routing Policy work?

Answer 2

• You can only have 1 record, it maps to multiple IP Addresses
• If you specify multiple values in a record, Route53 returns all values in random order

Question 3

When using Simple Routing Policy, why will two requests to the same server back-to-back always return the same IP address twice?

Answer 3

DNS cacheing

On the first request, the server is randomly selecting which IP address the record should map to (in accordance with the simple routing policy), and then cacheing that value for the TTL

But on the second request, DNS is just going to the cache,

To get a new random value, you will either need to flush the DNS cache or wait the TTL.

Question 4

How does Amazon’s Weighted Routing Policy work?

Answer 4

• Allows you to split traffic based on different weights assigned
  
  • (E.g. you can send 10% of your traffic to US-EAST-1 and the other 90% to EU-WEST-1)

Question 5

How do Health Checks factor in to Route53 routing?

Answer 5

• You can set up health checks on individual record sets
• If a record set fails a health check, it will be removed from Route53 until it passes the health check
• you can set up SNS notifications to alert you if a health check is failed.

Question 6

When using a weighted routing policy, should your inputted weights be numerators or percentages?

Answer 6

Numerators

Question 7

How does Route53 Latency-based Routing work?

Answer 7

• It allows you to route your traffic to the region with the fastest response time
• To use it, you need to create a latency resource record set for the EC2 (or ELB) resource in each region that hosts your website.

Question 8

How does Route53’s Failover Routing Policy work?

Answer 8

• Designed for when you want an active/passive setup (Disaster Recovery)
• You pick a primary and a secondary site, Route53 monitors the health of your primary instance using health checks, and if primary goes down, Route53 automatically switches traffic over to the secondary site.

Question 9

How does Route53’s Geolocation Routing Policy work?

Answer 9

• Choose where your traffic is sent based on the geographic location of the user (i.e. the location from which the DNS queries originate)
• Idea: PHYSICAL LOCATION NOT LATENCY

Question 10

At a high level, how does Route53’s Geoproximity Routing work?

Answer 10

• route traffic based on geographaic location of users AND locations
• You can also optionally choose to route more/less traffic to a given resource by specifying a bias, which expands/shrinks the size of the geographic region from which traffic is routed to a resource
• To use geoproxminity routing, you must use Route53 traffic flow

Question 11

How does Route53’s Multivalue Answer Policy work?

Answer 11

• Route53 can return multiple values, such as IP addresses for your wbe servers, in response to DNS queries.
• You can specify multiple values for almost any record, but multivalue answer routing also lets you check the health of each resource, so Route 53 returns only values for healthy resources
• Just like simple routing, but you can put health checks on each record set and filter for only healthy resources.