ACP-Cloud1 Exam Dumps : ACP Cloud Computing Certification

When the black hole policy is triggered by excessive DDoS traffic, the affected server is temporarily isolated from the network to prevent further damage. During this period, no services are available, meaning the server cannot provide limited-speed services.

The X-Forwarded-For field in HTTP header is used to identify the originating IP address of a client connecting to a web server through an HTTP proxy or a load balancer. When the “Obtain the Visitor’s Real IP Address” function is enabled in Alibaba Cloud SLB, the SLB instance adds the X-Forwarded-For field to the HTTP header of each request and forwards the request to the backend server. The backend server can then obtain the real IP address of the visitor from the X-Forwarded-For field1. The format of the X-Forwarded-For field is as follows:

X-Forwarded-For: client, proxy1, proxy2

where the value is a comma+space separated list of IP addresses, the left-most being the original client, and each successive proxy that passed the request adding the IP address where it received the request from. In this example, the request passed through proxy1, proxy2, and then the SLB instance (proxy3).2

References: Obtain client IP addresses - Server Load Balancer - Alibaba Cloud, X-Forwarded-For - MDN Web Docs

Using lifecycle hooks in Auto Scaling allows for custom operations, such as updating the Redis whitelist when instances are added or removed. An OOS (Operation Orchestration Service) template can automate this process, and MNS (Message Notification Service) can trigger events to inform Redis when changes occur.

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