Multi-Site GSLB with Failover

VCF 9.0Intermediatespecialist⏱ 105 min

Objectives

Configure global load balancing across 3 datacenters; verify geo-routing; test failover.

Prerequisites

VCF lab environment deployed and operational

Lab Environment

Standard VCF lab environment for Avi Load Balancer 30.x Specialist

Tasks

Task 1 Multi-Site GSLB with Failover

Configure global load balancing across 3 datacenters; verify geo-routing; test failover.

Step 1

Configure GSLB Pool (on Primary Controller):

Step 2

Create GSLB Service (Global VS):

Step 3

Verify GSLB Replication to Secondary Sites:

Step 4

Test Geo-Routing (Simulate Client IPs):

Step 5

Simulate Failure (app-east pool down):

Step 6

Restore Service (app-east back online):

Step 7

Validation Checklist: GSLB replication active on all 3 sitesGeo-routing returns correct pools per regionFailover to backup pool when primary DOWNAutomatic fallback when primary restoredTTD < 15 sec; DNS TTL working as expected (60 sec)

Validation Gate

Check: Verify lab completion

Expected: Lab exercise completed successfully

Common Errors

GSLB DNS delegation not configured on authoritative DNS server

Fix: Avi GSLB requires DNS delegation: the authoritative DNS for the domain must delegate the GSLB subdomain (e.g., app.example.com) to the Avi DNS Virtual Service. Without delegation, GSLB health checks work but clients never query Avi DNS. Verify: nslookup app.example.com should return Avi DNS VS IP as the authoritative server.

GSLB site health monitor using wrong probe method

Fix: GSLB health monitors probe the local Virtual Service at each site. If the VS uses HTTPS but the GSLB health monitor uses HTTP, the probe fails (redirect or connection refused). Match GSLB health monitor protocol to the actual VS protocol. Use HTTPS health monitor with appropriate SSL profile.

Failover not working because GSLB priority/ratio not configured

Fix: Avi GSLB supports: active/standby (priority-based), active/active (round-robin or geo-based), and ratio-based distribution. Without explicit configuration, default is round-robin across all sites. For DR failover: set primary site priority=1, DR site priority=2 with fallback algorithm.

Final Validation

Lab completed successfully

✓ All steps completed → No errors observed

Cleanup / Restore

• Revert to snapshot if needed

Design Reflection (VCDX)

GSLB design demonstrates multi-site application delivery architecture. VCDX panelists test DNS delegation, health monitoring, and failover behavior across sites.

⚠ Known Pitfalls (from Community KB)

Deploying GSLB without DNS delegation — health checks pass but no client traffic reaches Avi.

Using round-robin when the intent is active/standby — both sites receive production traffic.

Mark complete