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F5 302: BIG-IP DNS and Global Traffic Reference
F5 302 is a historical reference associated with BIG-IP DNS and global traffic-management concepts. It concerns decisions made before an application connection reaches a local delivery service: how a name is resolved, which site or service should receive a user, what health evidence supports that choice and how DNS behavior affects availability. Current F5 program names may differ, so this page should be used as a study reference rather than evidence of active exam availability.
Use the official F5 certification catalog to verify current paths, prerequisites and registration conditions.
Global traffic-management concepts
DNS as a service-entry decision
DNS is part of the user experience and the availability design. A response can determine which address or site a client contacts, while caching and time-to-live behavior influence how quickly a change becomes visible. Study authoritative DNS, recursive resolution, records, delegation, response timing and the operational effect of stale or incorrect information. Diagnose from the client perspective as well as from the DNS infrastructure.
Global server load balancing
Global load balancing selects among sites or services using factors such as health, topology, capacity, persistence, geographic proximity or business policy. The right answer depends on the goal: nearest is not always healthiest, and a healthy site may not be suitable for a user's data or service requirement. Document the selection logic so that teams can explain and test failover behavior.
Health and availability
Global decisions depend on credible health evidence. A monitor should reflect the condition required for a user transaction, not merely whether a network endpoint answers. Consider dependencies, response content, timing, maintenance state and the behavior when monitoring itself is uncertain. High availability also requires redundant DNS infrastructure, configuration synchronization, change control and tested recovery procedures.
Topology and policy
Topology-based selection can support latency, regional service design, regulatory constraints and disaster recovery. It must be maintained as networks, sites and customer needs change. Policies should be clear about precedence, fallback and exceptions. Overly complex topology logic can create a failure that is difficult to reproduce or communicate during an incident.
DNS security and troubleshooting
DNS services need controlled administration, logging, protection against unauthorized changes and careful management of records and keys. When a global service problem occurs, collect evidence from client resolution, authoritative responses, health status, selection logs, network reachability and application availability. Separate a DNS response issue from a backend outage, certificate problem or local-delivery failure before changing a policy.
Who can use this reference
This material is useful for DNS administrators, network engineers, application-delivery teams, SREs and service owners who need to design or troubleshoot multi-site application access. It is valuable even outside F5 environments because DNS and global routing principles transfer across platforms.
A practical study sequence
- Map a multi-site application from a user's DNS query through local delivery and the backend service.
- Define health checks for each site and test a controlled site failure with documented fallback behavior.
- Compare two selection policies against latency, data location and capacity requirements.
- Observe client caching and TTL effects during a planned response change.
- Write an incident runbook that distinguishes DNS, global-selection, local-load-balancing and application failures.
Before scheduling
Confirm whether a successor or equivalent F5 DNS path is active, then verify all delivery and pricing details directly with F5. Historic question counts, scores and duration are not reliable current information.
Frequently asked questions
Why is DNS important to availability?
It often determines the first service destination a client uses, so incorrect or stale DNS behavior can prevent users from reaching an otherwise healthy application.
Does global traffic management replace local load balancing?
No. Global decisions choose among sites or services; local delivery typically manages traffic to targets within the selected site.
Where can I verify current F5 certification status?
Use F5's current certification catalog before enrollment or scheduling.