The Citrix NetScaler initially selects a server by using a load balancing method. With persistence configured, enabling the NetScaler to send any subsequent client requests to the selected server, the server can access state information for that client. If persistence is configured, it overrides the load balancing methods once the server has been selected.
If the configured persistence applies to a service that is down, the NetScaler uses the load balancing methods to select a new service, and the new service becomes persistent for subsequent requests from the client. If the state of the selected service is “out of service”, it continues to serve the outstanding requests, but it does not allow new requests or connections. After the shutdown period elapses, no new requests or connections are directed to the service and the existing connections are closed.
This persistence type is used with link load balancing. With destination IP addresses (DESTIP) configured, the NetScaler chooses a service based on the configured load balancing method. It then directs all subsequent packets to the selected service based on the DEST IP. To configure persistence based on destination IP addresses, in the Persistence list, select DESTIP.
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