F5 Global Server Load Balancing (GSLB)
Load balancing software
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What is F5 Global Server Load Balancing (GSLB)
F5 Global Server Load Balancing (GSLB) is a DNS-based load balancing capability used to distribute application traffic across multiple data centers or cloud regions. It helps network and application teams steer users to the best available site based on health checks, proximity, and policy, and it supports failover for disaster recovery scenarios. GSLB is commonly delivered as part of F5 BIG-IP DNS (formerly GTM) and integrates with other BIG-IP services for application delivery and security.
Multi-site resiliency and failover
GSLB supports active-active and active-standby patterns across geographically distributed sites using DNS responses. It can automatically steer traffic away from unhealthy sites based on health monitors and availability signals. This is useful for disaster recovery and for maintaining service continuity during regional outages.
Policy-based traffic steering
The product supports multiple decision inputs such as topology/geolocation, round-robin, and health-based logic to influence DNS answers. Teams can implement routing policies for different applications, user regions, or service tiers. This provides more control than basic DNS failover configurations.
Integrates with BIG-IP ecosystem
When deployed with BIG-IP, GSLB can reuse shared objects such as monitors, iRules-based logic (where applicable), and operational tooling. It can integrate with application delivery and security services in the same platform, reducing the number of separate appliances to manage. This can simplify operations for organizations already standardized on F5.
DNS-based control limitations
Because GSLB relies on DNS, traffic steering is influenced by DNS caching and TTL behavior outside the organization’s control. Client resolvers and intermediate DNS infrastructure can cause slower convergence during failover than connection-level load balancing. Some user traffic may continue to reach a degraded site until caches expire.
Operational complexity and expertise
Designing and operating multi-site DNS load balancing requires careful planning around monitors, topology rules, and delegation/authoritative DNS architecture. Misconfiguration can lead to suboptimal routing or unintended failover behavior. Organizations often need specialized network expertise to run it reliably at scale.
Platform and licensing dependency
GSLB is typically consumed through the BIG-IP DNS product and associated licensing, which can increase total cost compared with lighter-weight or software-only approaches. Deployments may require dedicated appliances or virtual editions and ongoing maintenance. This can be less attractive for teams seeking cloud-native, self-managed tooling with minimal vendor lock-in.
Plan & Pricing
| Plan | Price | Key features & notes |
|---|---|---|
| Subscription (1–3 year) | Not listed — contact F5 Sales | F5 subscription option; includes version updates, maintenance & support (per F5 “Get F5” buying options). |
| Perpetual License (GBB) | Not listed — contact F5 Sales | Perpetual licensing option referenced on F5 site (GBB). |
| Flex Consumption / Cloud Marketplace (PAYG) | Not listed — contact F5 Sales | F5 references pay-as-you-go marketplace offerings and Flex consumption program; actual marketplace fees are not published on f5.com. |
Notes: F5’s public product pages (BIG-IP DNS / GSLB) and "Get F5" purchasing pages do not publish list prices for BIG-IP DNS / GSLB; they direct customers to contact F5 sales or use cloud marketplaces.
Seller details
F5, Inc.
Seattle, Washington, USA
1996
Public
https://www.f5.com/
https://x.com/f5
https://www.linkedin.com/company/f5/
