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You can configure BIG-IP Global Traffic Manager (GTM) to provide static persistence of local DNS servers to virtual servers. You can accomplish this by configuring GTM to perform Static Persist load balancing. With this configuration, GTM guarantees that certain transactions are routed through a single transaction manager (for example, Local Traffic Manager or other server array manager). This is beneficial for transaction-oriented traffic, such as e-commerce shopping carts, online trading, and online banking.
The Static Persist load balancing method uses the persist mask with the source IP address of the LDNS in a deterministic algorithm to send requests to a specific pool member (virtual server). Using this method, BIG-IP GTM sends DNS name resolution requests to the first available pool member based on a hash algorithm that determines the order of the pool members. This algorithm orders the pool members differently for each LDNS that is sending requests to BIG-IP GTM, taking into account the Classless Inter-Domain Routing (CIDR) of the LDNS. As BIG-IP GTM distributes requests across all pool members, requests from each LDNS (and thus, each client) are generally sent to the same pool member. When the selected pool member becomes unavailable, BIG-IP GTM sends requests to another pool member. When the original pool member becomes available again, BIG-IP GTM sends requests to that pool member.