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Difficulty: HardDesign Traffic Routing and Failover Strategies

An organization is designing a high-availability architecture across the East US and West US regions. The design uses Azure Front Door to route client traffic to web applications and Azure Traffic Manager to route DNS requests for regional API gateways. The target Recovery Time Objective (RTO) for any endpoint failover event is less than 2 minutes. You need to configure the failover detection and routing parameters for both services to meet the RTO while minimizing false-positive failovers. Which two configurations should you recommend? (Select TWO.)

  1. For Azure Traffic Manager, set the DNS Time-to-Live (TTL) to 30 seconds, and configure the health probing interval to 10 seconds.Answer
  2. For Azure Front Door, configure health probes with an interval of 5 seconds using HTTP or HTTPS protocols to detect endpoint failures.Answer
  3. C
    For Azure Traffic Manager, configure SSL termination and URL path-based routing rules to direct traffic to healthy endpoints based on the incoming request URI.
  4. D
    For Azure Front Door, configure health probes to use raw TCP ping probes on port 443 to monitor endpoint availability while reducing backend load.

Answer

The correct configuration is to set the Azure Traffic Manager DNS Time-to-Live (TTL) to 30 seconds and the health probing interval to 10 seconds, and to configure the Azure Front Door health probes with an interval of 5 seconds using HTTP or HTTPS protocols.
The correct strategy combines configuring Azure Traffic Manager with a low DNS TTL of 30 seconds and a 10-second probing interval to satisfy DNS propagation time constraints, and configuring Azure Front Door with short 5-second health probes using HTTP/HTTPS. These settings ensure that both DNS-based and application-level routing layers failover within the required 2-minute threshold.

Step-by-Step Solution

1
Analyze the recovery time objective (RTO) constraint.
The target RTO is less than 2 minutes, requiring both DNS caching and health probe intervals to react within this window.
Default TTL settings (300 seconds for Traffic Manager) would cause clients to cache outdated IP addresses for up to 5 minutes, violating the RTO.
2
Evaluate Azure Traffic Manager settings for fast failover.
Reducing DNS TTL to 30 seconds and setting the probing interval to 10 seconds allows Traffic Manager to detect failures and propagate DNS updates within 40 seconds.
This satisfies the RTO and utilizes the supported Fast Failover capability of Traffic Manager.
3
Evaluate Azure Front Door health probe requirements.
Front Door must use HTTP or HTTPS probes. Setting the interval to 5 seconds ensures failover detection happens in seconds.
Front Door is an application-layer service that does not support raw TCP health probes.
4
Eliminate unsupported configurations.
Eliminated SSL termination on Traffic Manager (DNS-only) and TCP ping on Front Door (unsupported).
This avoids architectural design errors where layer-4 DNS solutions are incorrectly assumed to have layer-7 application awareness.

Key Concept

Designing multi-region traffic routing requires configuring low DNS TTLs and fast health probe intervals to meet tight RTO targets, while respecting protocol limitations of DNS-based versus application-level routing services.
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Topics

Design Traffic Routing and Failover Strategies

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