Default Predictor for Selecting Best Server on ACE for Client Requests | 400-251 Exam Answer

Default Predictor on ACE for Server Selection

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Which option describes the default predictor on ACE to select the best server to fulfill a client request?

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A. B. C. D.

C.

ACE (Application Control Engine) is a Cisco load balancer that distributes incoming network traffic across multiple servers to improve application availability and performance. When a client request comes in, ACE selects the best server to fulfill the request based on a load-balancing algorithm. The load-balancing algorithm is configured on ACE as a predictor.

The default predictor on ACE is the "round robin" algorithm. Round-robin load balancing distributes incoming requests equally across all available servers. The algorithm selects the next server in the list of real servers for each new request. This ensures that all servers receive an equal amount of traffic, which can help prevent overloading of a single server.

However, the default predictor can be changed on ACE to one of several other algorithms, depending on the requirements of the application being load-balanced. The available predictors include:

  • Hash cookie: This algorithm selects the server by using a hash value that is based on a cookie name. The cookie is set by the server in the response to the client's request. When subsequent requests come in from the same client, ACE uses the cookie to determine which server should handle the request. This can be useful for applications that require session persistence, as it ensures that all requests from a particular client are always handled by the same server.

  • Least bandwidth: This algorithm selects the server that has processed the least amount of network traffic. This can be useful for applications that have servers with varying capacities, as it ensures that requests are sent to the least busy server.

  • Hash DNS: This algorithm selects the server using a hash value that is based on the fully qualified domain name (FQDN). This can be useful for applications that use multiple DNS entries for a single IP address, as it ensures that requests are sent to the correct server based on the FQDN.

In summary, the default predictor on ACE is the round-robin algorithm, but there are several other predictors available that can be configured based on the requirements of the application being load-balanced.