Implementing Radware Alteon Global Load Balancing with DNS Health Checks
Global server load balancing (GSLB) is useful when an application runs across multiple Australian and international data centres. Radware Alteon can direct users to the most suitable site by combining DNS responses, service health, proximity, and availability rules. This provides a practical way to manage active-active or active-standby application deployments.
DNS health checks are central to that design. Alteon periodically tests virtual services at each site and removes an unhealthy location from DNS answers before users continue receiving failed connections. The result depends on careful planning: DNS caching, monitoring intervals, application dependencies, and traffic policies all affect failover behaviour.
Australian organisations also need to account for distance between Sydney, Melbourne, Perth, and overseas regions. A policy that looks sensible in a lab may produce different results for users on corporate networks, mobile providers, or residential broadband connections. The following design focuses on predictable operation, clear troubleshooting, and controlled change management.
| Design area | Recommended approach | Operational consideration |
|---|---|---|
| DNS role | Use Alteon GSLB as the authoritative decision point or integrate it with the existing DNS architecture | Confirm delegation, TTLs, and resolver behaviour before production |
| Health validation | Test the application virtual service with TCP, HTTP, HTTPS, or content-aware checks | A port can be open while the application is unusable |
| Traffic policy | Start with proximity or site preference, then add persistence and weighting where required | Geographic accuracy varies between recursive DNS resolvers |
| Failure handling | Remove failed sites from responses and retain a tested fallback | Define what happens when every site is unhealthy |
| Change control | Lower TTL before migration and restore it after validation | Cached records can delay visible failover |
Map the application and DNS architecture
Begin by documenting each Alteon site, public IP address, virtual server, pool, and backend dependency. Record which services are global, which remain local, and whether sessions can move between sites. A web tier may fail over cleanly while a database, payment gateway, identity provider, or file service still depends on the original location.
The DNS path deserves equal attention. Identify the parent zone, delegated GSLB subdomain, authoritative name servers, recursive resolvers, and any traffic-management platform in front of Alteon. In a hybrid environment, AWS Route 53, Azure DNS, on-premises DNS, and Alteon can coexist, but ownership of each record must be unambiguous.
For Australian deployments, test name resolution from at least Sydney, Melbourne, and Perth. A resolver in Perth may receive a different answer from a resolver in Sydney, while a public recursive service may place users according to resolver location rather than the end device. This is important when a business serves customers nationally from two eastern data centres.
Configure sites, services, and health monitors
Create a GSLB site object for each participating location and associate the relevant virtual server or service group. Use descriptive names that expose the role and location, such as WEB-SYD-PROD and WEB-MEL-PROD. Consistent naming makes command-line output and event logs easier to interpret during an incident.
Select the least complex monitor that proves the service is usable. A TCP check confirms that a listener accepts connections, while an HTTP or HTTPS check can validate the response code, host header, URI, and expected content. For an application with a login page, health endpoint, or API status path, use a purpose-built endpoint that does not trigger a transaction.
Set sensible intervals, timeouts, and failure thresholds. A very aggressive monitor can create unnecessary site flapping during packet loss; a slow monitor can leave a failed location in DNS answers for too long. Monitor from the Alteon perspective and verify that firewall rules, reverse paths, certificates, and virtual hosting settings permit the probe.
Build the DNS decision policy
The GSLB policy should reflect business intent rather than simply distributing records evenly. Proximity rules can direct Australian users to the closest healthy site, while weighted distribution supports staged migrations or capacity differences. Active-standby designs should express a clear primary and backup order.
DNS answers are cached by recursive resolvers and clients according to TTL. Lowering the TTL helps during a planned migration, but it cannot guarantee immediate convergence because some resolvers cache beyond the stated value. Keep TTLs practical for normal operation and document the expected failover window instead of promising instant redirection.
Avoid treating DNS GSLB as a replacement for connection-level load balancing. Alteon still needs to balance traffic within each selected site. Review how DNS answers interact with browser caching, corporate resolvers, IPv4 and IPv6 records, and clients that reuse existing connections.
Validate failure and recovery paths
Test each failure domain separately. Stop the application process, block the service port, return an unhealthy HTTP status, and disconnect a site from the network. Confirm that the monitor changes state, the site is removed or deprioritised, and new DNS queries receive the intended alternative address.
Recovery testing is equally important. Restore the service and observe whether Alteon marks it healthy only after the configured success threshold. Check that traffic does not return too quickly while dependent services are still starting. Capture DNS responses with dig, nslookup, or a monitoring platform from multiple Australian networks.
Application behaviour must be tested during a live transition. If sessions are stored locally, users may be sent to a healthy site that lacks their session state. Cookie persistence, shared session storage, and idempotent retry logic need to be designed with GSLB in mind. Similar symptoms can occur with cloud load balancers, so this AWS 503 troubleshooting reference is useful when separating backend failure from routing failure.
Monitor operations and troubleshoot anomalies
Collect Alteon health status, DNS query results, monitor latency, pool member state, and configuration changes in a central logging platform. Alerts should identify the site, virtual service, monitor type, and reason for failure. “Service down” is much less useful than “HTTPS content check failed for /healthz because the expected response marker was absent.”
When users report intermittent failures, compare authoritative answers with responses from their recursive resolver. Check TTL, EDNS behaviour, split-horizon records, DNSSEC validation, and whether an old address remains cached. Also verify that a firewall or upstream provider is not dropping traffic only from one monitoring location.
Plan maintenance around Australian operating patterns. Retail, healthcare, and public-sector systems may have strict after-hours windows, while nationally distributed teams often perform changes outside Sydney business hours to reduce disruption elsewhere. Use a runbook with rollback commands, exported configuration, and a named owner for DNS delegation and Alteon policy changes.
Apply security, compliance, and change controls
Protect the management plane with role-based access, multifactor authentication where supported, restricted administration networks, and audited configuration backups. Health-check endpoints should reveal only the status needed for monitoring; they should not expose version information, credentials, or internal dependency details.
Review data flows under the Privacy Act and Australian Privacy Principles when DNS routing sends users or application data offshore. The location of logs, health-check responses, session stores, and analytics data may matter even when the public service appears Australian. Organisations handling regulated information should also align operational controls with their internal security framework and relevant Australian Signals Directorate guidance.
Use staged changes: export the current configuration, lower DNS TTL if required, add one site or policy change, test from several networks, and monitor before proceeding. After stabilisation, restore the normal TTL and record the final behaviour. This disciplined process makes Alteon GSLB a dependable part of a hybrid infrastructure rather than an opaque emergency switch.