Azure Traffic Manager

How Traffic Manager Works

Traffic Manager is pure DNS routing — it never sees your actual traffic. Here's what happens:

1. User types app.contoso.com in their browser
2. DNS resolves app.contoso.com to Traffic Manager's DNS name
3. Traffic Manager evaluates its routing policy and health of endpoints
4. Traffic Manager returns the DNS name of the best endpoint (e.g., contoso-eastus.azurewebsites.net)
5. User's browser connects directly to that endpoint
6. Traffic Manager is no longer involved — all traffic goes directly to the endpoint

Profiles and Endpoints

A Traffic Manager profile defines the routing method and contains endpoints. Endpoints are the destinations traffic is routed to. Three endpoint types:

Six Routing Methods

1. Priority

All traffic goes to the primary endpoint. If it fails health checks, traffic fails over to the secondary. Best for active-passive disaster recovery.

Priority 1: East US (primary — all normal traffic)
Priority 2: West Europe (secondary — only if East US fails)

2. Weighted

Traffic is distributed across endpoints based on assigned weights. Used for gradual rollouts, A/B testing, or distributing load proportionally.

East US — Weight 90 (90% of traffic)
West US — Weight 10 (10% of traffic — canary)

3. Performance

Routes users to the endpoint with the lowest network latency — typically the closest geographic region. Best for globally distributed applications where performance matters most.

4. Geographic

Routes users based on their geographic location. Users in India → India endpoints, users in Europe → European endpoints. Used for data sovereignty, content localisation, and compliance requirements.

5. Multivalue

Returns multiple healthy endpoint IPs in a single DNS response. The client picks one. Only works with IPv4/IPv6 endpoints (not nested profiles). Increases availability — even if one endpoint fails, the client has alternatives.

6. Subnet

Maps specific source IP address ranges to specific endpoints. Useful for directing traffic from your corporate network to a specific backend, or A/B testing by IP range.

Health Monitoring

Traffic Manager monitors endpoint health by sending periodic HTTP/HTTPS/TCP probes to a configured path. If an endpoint fails health checks, Traffic Manager stops returning it in DNS responses until it recovers.

Nested Profiles

Nested profiles allow complex routing scenarios — a parent profile routes between regions, and child profiles handle routing within each region:

Parent profile (Geographic routing):
  Asia users → Asia child profile (Performance routing between India/Singapore)
  Europe users → Europe child profile (Performance routing between UK/Germany)

Limitations of DNS Routing

• No SSL termination — Traffic Manager doesn't touch HTTP/HTTPS
• No WAF — No web application firewall capability
• No CDN caching — Only DNS routing, no content delivery
• Failover limited by DNS TTL — Not instant failover like Front Door
• No URL path routing — Routes at the domain level, not URL path level
• Client DNS caching — Clients may cache DNS responses beyond TTL

Traffic Manager vs Front Door

Real-World Use Cases