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Failover routing for disaster recovery in AWS - Cheat Sheet & Quick Revision

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Recall & Review
beginner
What is failover routing in the context of disaster recovery?
Failover routing automatically switches traffic from a primary site to a backup site when the primary site fails, ensuring continuous service availability.
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beginner
Which AWS service is commonly used to implement failover routing?
Amazon Route 53 is used to implement failover routing by monitoring health checks and routing traffic to healthy endpoints.
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intermediate
What role do health checks play in failover routing?
Health checks monitor the status of the primary endpoint. If the health check fails, Route 53 routes traffic to the secondary endpoint.
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intermediate
What is the difference between active-passive and active-active failover routing?
Active-passive routing sends traffic to the primary site until it fails, then switches to the backup. Active-active routing sends traffic to multiple sites simultaneously for load sharing and redundancy.
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intermediate
Why is DNS TTL important in failover routing?
DNS TTL (Time to Live) controls how long DNS responses are cached. A low TTL helps faster failover by reducing caching time, so clients get updated routing quickly.
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Which AWS service helps route traffic during failover?
AAmazon S3
BAmazon Route 53
CAWS Lambda
DAmazon EC2
What triggers failover routing to switch traffic to a backup site?
AHealth check failure
BUser request
CManual DNS update
DScheduled maintenance
In failover routing, what does a low DNS TTL value help with?
AIncreased latency
BLonger caching
CFaster traffic switching
DSlower DNS resolution
Which failover routing type sends traffic to multiple sites at the same time?
AManual failover
BActive-passive
CStatic routing
DActive-active
What is the main purpose of failover routing?
AEnsure service availability during failures
BIncrease DNS caching
CReduce server load
DBackup data storage
Explain how failover routing works in AWS for disaster recovery.
Think about how Route 53 monitors and switches traffic when a site fails.
You got /4 concepts.
    Describe the difference between active-passive and active-active failover routing.
    Consider how traffic is distributed in each method.
    You got /4 concepts.

      Practice

      (1/5)
      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
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