Failover routing for disaster recovery in AWS - Step-by-Step Execution

Process Flow - Failover routing for disaster recovery

User DNS Request

↓

Check Primary Site Health

↓

Healthy

User DNS requests are checked against the primary site health. If healthy, traffic routes there; if not, traffic fails over to the secondary site.

Execution Sample

AWS

Route53 failover record setup:
Primary: IP 10.0.0.1, Health check
Secondary: IP 10.0.1.1, no health check
DNS routes based on health

This setup routes user traffic to the primary IP if healthy, else to the secondary IP for disaster recovery.

Process Table

Step	Primary Site Health	DNS Route	User Request Outcome
1	Healthy	Primary IP (10.0.0.1)	Request served by Primary
2	Healthy	Primary IP (10.0.0.1)	Request served by Primary
3	Unhealthy	Secondary IP (10.0.1.1)	Request served by Secondary
4	Unhealthy	Secondary IP (10.0.1.1)	Request served by Secondary
5	Healthy	Primary IP (10.0.0.1)	Request served by Primary

💡 Failover routing switches DNS to secondary IP when primary health check fails, and switches back when primary recovers.

Status Tracker

Variable	Start	After Step 1	After Step 3	After Step 5
Primary Site Health	Healthy	Healthy	Unhealthy	Healthy
DNS Route	Primary IP	Primary IP	Secondary IP	Primary IP
User Request Outcome	N/A	Primary serves	Secondary serves	Primary serves

Key Moments - 2 Insights

Why does DNS route to the secondary IP only when the primary site is unhealthy?

Because Route53 failover routing uses health checks to detect primary site status. When health check fails (see execution_table step 3), DNS switches to secondary IP to maintain service availability.

What happens when the primary site recovers after being unhealthy?

As shown in execution_table step 5, once the primary site health check passes again, DNS routes back to the primary IP automatically to restore normal traffic flow.

Visual Quiz - 3 Questions

Look at the execution_table, what is the DNS route at step 3?

A Primary IP (10.0.0.1)

B Secondary IP (10.0.1.1)

C No route

D Both Primary and Secondary

💡 Hint

Check the 'DNS Route' column at step 3 in the execution_table.

At which step does the user request get served by the secondary site?

A Step 1

B Step 2

C Step 3

D Step 5

💡 Hint

Look at the 'User Request Outcome' column in the execution_table.

If the primary site never recovers, how would the DNS route change after step 3?

A Stay on Secondary IP

B Alternate between Primary and Secondary

C Switch back to Primary IP immediately

D No DNS route

💡 Hint

Refer to the failover logic in concept_flow and execution_table steps 3 and 4.

Concept Snapshot

Failover routing uses DNS health checks to detect if the primary site is down.
If unhealthy, DNS routes traffic to a secondary site.
When primary recovers, DNS switches back automatically.
This ensures continuous service availability during disasters.

Full Transcript

Failover routing for disaster recovery means directing user traffic to a backup site if the main site fails. Route53 uses health checks to monitor the primary site. When healthy, DNS sends users there. If the primary site becomes unhealthy, DNS automatically routes users to the secondary site to keep the service running. When the primary site recovers, traffic switches back. This process helps avoid downtime during failures.

Practice

1. What is the main purpose of failover routing in disaster recovery?

easy

A. To block all traffic during maintenance

B. To increase the speed of the primary server

C. To reduce the cost of cloud services

D. To automatically send users to a backup server if the main server fails

Solution

1. Step 1: Understand failover routing purpose

   Failover routing is designed to keep services available by switching traffic to a backup if the main server fails.

2. Step 2: Eliminate unrelated options

   Options about speed, cost, or blocking traffic do not describe failover routing's main goal.

3. Final Answer:

   To automatically send users to a backup server if the main server fails -> Option D

4. Quick Check:

   Failover routing = automatic backup switch [OK]

Hint: Failover means switch to backup when main fails [OK]

Common Mistakes:

• Confusing failover with performance improvement
• Thinking failover blocks traffic
• Assuming failover reduces costs

2. Which AWS Route 53 routing policy is used to implement failover routing?

easy

A. Geolocation routing policy

B. Latency routing policy

C. Failover routing policy

D. Weighted routing policy

Solution

1. Step 1: Identify routing policies in Route 53

   Route 53 offers several routing policies, including latency, geolocation, weighted, and failover.

2. Step 2: Match failover routing policy to disaster recovery

   Failover routing policy is specifically designed to route traffic to a backup when the primary fails.

3. Final Answer:

   Failover routing policy -> Option C

4. Quick Check:

   Failover routing policy = failover setup [OK]

Hint: Failover routing policy is named for failover use [OK]

Common Mistakes:

• Choosing latency or weighted policies for failover
• Confusing geolocation with failover
• Not knowing Route 53 routing policy names

3. Given this Route 53 failover setup: Primary health check fails, what happens to user traffic?
Primary: IP 10.0.0.1 (health check enabled)
Secondary: IP 10.0.0.2 (backup)

medium

A. Traffic switches to secondary IP 10.0.0.2

B. Traffic is split evenly between primary and secondary

C. Traffic is blocked until primary recovers

D. Traffic continues to primary IP 10.0.0.1

Solution

1. Step 1: Understand health check failure effect

   If the primary health check fails, Route 53 detects the primary is unhealthy.

2. Step 2: Apply failover routing behavior

   Failover routing sends traffic to the secondary (backup) IP when primary is unhealthy.

3. Final Answer:

   Traffic switches to secondary IP 10.0.0.2 -> Option A

4. Quick Check:

   Primary down = traffic to backup [OK]

Hint: Failover sends traffic to backup if primary fails health check [OK]

Common Mistakes:

• Assuming traffic stays on primary despite failure
• Thinking traffic is blocked during failover
• Believing traffic splits evenly without weighting

4. You configured failover routing but traffic never switches to the backup server during primary failure. What is the most likely cause?

medium

A. Latency routing policy is used instead of failover

B. Health check is not associated with the primary record

C. Backup server IP address is incorrect

D. TTL value is set to zero

Solution

1. Step 1: Check health check association

   Failover routing requires the primary record to have a health check to detect failure.

2. Step 2: Understand impact of missing health check

   If the health check is missing or not linked, Route 53 never detects primary failure, so no failover occurs.

3. Final Answer:

   Health check is not associated with the primary record -> Option B

4. Quick Check:

   Failover needs health check linked to primary [OK]

Hint: Failover needs health check linked to primary record [OK]

Common Mistakes:

• Ignoring health check association
• Blaming backup IP without checking health check
• Confusing routing policies
• Misunderstanding TTL effects

5. You want to design a disaster recovery setup using Route 53 failover routing with two regions: primary in us-east-1 and backup in us-west-2. Which configuration ensures automatic failover with minimal downtime?

hard

A. Create two records with failover routing; primary record with health check in us-east-1, secondary record without health check in us-west-2

B. Create two records with weighted routing; assign 100% weight to primary and 0% to backup

C. Create two records with geolocation routing; route us-east traffic to primary and us-west traffic to backup

D. Create two records with latency routing; primary in us-east-1 and backup in us-west-2

Solution

1. Step 1: Understand failover routing setup

   Failover routing requires a primary record with a health check and a secondary record without a health check as backup.

2. Step 2: Evaluate options for disaster recovery

   Create two records with failover routing; primary record with health check in us-east-1, secondary record without health check in us-west-2 correctly sets primary with health check and backup without health check, enabling automatic failover.

3. Step 3: Eliminate other options

   Weighted routing does not provide automatic failover; geolocation routes by location, not health; latency routing routes by speed, not failure.

4. Final Answer:

   Create two records with failover routing; primary record with health check in us-east-1, secondary record without health check in us-west-2 -> Option A

5. Quick Check:

   Failover needs primary health check and backup record [OK]

Hint: Primary needs health check; backup record no health check [OK]

Common Mistakes:

• Using weighted routing instead of failover
• Assigning health check to backup record
• Confusing geolocation with failover
• Expecting latency routing to handle failover