Global Server Load Balancing (GSLB) allows you to efficiently distribute network traffic across multiple servers located in different geographical locations or multiple subnets. This enables you to enhance the scalability, availability, and performance of your network by directing clients to the most suitable server based on various factors, such as health and network relevance conditions.
The BlueCat Edge GSLB service is based on rule-based policies and tailors DNS responses
before forwarding them to the clients by examining the query data and metadata of the
DNS query question and response. DNS answers are dynamically modified based on
configured rules to ensure optimal traffic distribution and performance. This is done
through two main components:
- GSLB rules—define matching criteria from client IP addresses specified in
CIDR blocks and IP lists, and query domains in listed domains or domain name
lists. When a query is made that matches the criteria, you can tailor the
answers using the following GSLB expert rules:
- Subnet-based ordering: You can configure the rules to reorder answers by defining prioritized matching subnets, or by removing unnecessary answers from the DNS query answer set with the same subnet matching conditions.
- Health check answers: Within the same rule, you can elevate the response by adding conditions of health checks to the ordering stack. With the health checks, if a query domain and IP address response match a health check monitor condition, you can exclude unhealthy answers and prioritize healthy answers.
- IP response limiting: Before wrapping the response and returning it back to the client, you can also limit the number of IP addresses within the response.
- Health check configurations—monitor specified endpoints for health to ensure that incoming DNS answers are correctly routed based on health conditions.
Attention: You must have the BlueCat Edge GSLB license
entitlements to create GSLB rules and health check configurations. Verify that you have
the correct licensing with your BlueCat Edge administrators before proceeding to
configure this feature.