ADC

Override persistence settings for overloaded services

September 14, 2021

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When a service is loaded or is otherwise unavailable, service to clients is degraded. In this case, you might have to configure the Citrix ADC appliance to temporarily forward to other services the requests that would otherwise be included in the persistence session that is associated with the overloaded service. In other words, you might have to override the persistence setting that is configured for the load balancing virtual server. You can achieve this functionality by setting the skippersistency parameter. When this skippersistence parameter is set, and if the virtual server receives new connections for an overloaded service, the following happens.

The virtual server disregards any existing persistence sessions that are associated with that service, until the service returns to a state at which it can accept requests.
Persistence sessions associated with other services are not affected.

This functionality is available for only virtual servers whose type is ANY or UDP.

In Branch Repeater load balancing configurations, you must also configure a load monitor and bind it to the service. The monitor takes the service out of subsequent load balancing decisions until the load on the service is brought below the configured threshold. For information about configuring a load monitor for your virtual server, see Understanding Load Monitors.

You can configure the virtual server to perform one of the following actions with the requests that would otherwise form a part of the persistence session:

Send each request to one of the other services. The virtual server takes a load balancing decision and sends each request to one of the other services based on the load balancing method. If all the services are overloaded, requests are dropped until a service becomes available.

Both wildcard and IP address–based virtual servers support this option. This action is appropriate for all deployments, including deployments in which the virtual server is load balancing Branch Repeater appliances or firewalls.
Bypass the virtual server-service configuration. The virtual server does not take a load balancing decision. Instead, it simply bridges each request through to a physical server based on the destination IP address in the request.

Only wildcard virtual servers of type ANY and UDP support the bypass option. Wildcard virtual servers have a : IP and port combination. This action is appropriate for deployments in which you are using the virtual server to load balance Branch Repeater appliances or firewalls. In these deployments, the Citrix ADC appliance first forwards a request to a Branch Repeater appliance or firewall, and then forwards the processed response to a physical server. The virtual server sends requests directly to their destination IP addresses in the following conditions.
- You configure the virtual server to bypass the virtual server–service configuration for overloaded services.
- The Branch Repeater appliance or firewall gets overloaded.
The virtual server sends requests directly to their destination IP addresses until the Branch Repeater appliance or firewall can accept requests.

To override persistence settings for overloaded services by using the CLI

At the command prompt, type the following commands to override persistence settings for overloaded services and verify the configuration:

set lb vserver <name> -skippersistency <skippersistency>

show lb vserver <name>
<!--NeedCopy-->

Example

> set lb vserver mylbvserver -skippersistency ReLb
 Done
> show lb vserver mylbvserver
    mylbvserver (*:*) - ANY Type: ADDRESS
      . . .
      . . .
 Skip Persistency: ReLb
      . . .
 Done
>
<!--NeedCopy-->

To override persistence settings for overloaded services by using the GUI

Navigate to Traffic Management > Load Balancing > Virtual Servers and select the virtual server of type UDP or ANY.
In the Advanced Settings pane, select Traffic Settings, and specify the type of Skip Persistency.

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Override persistence settings for overloaded services

September 14, 2021

Contributed by:

September 14, 2021

Contributed by:

Override persistence settings for overloaded services

To override persistence settings for overloaded services by using the CLI

Example

To override persistence settings for overloaded services by using the GUI

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