The statement is TRUE, with an important implementation distinction. Huawei Cloud extended network interfaces provide flexible networking independently of the ECS primary network interface. An extended network interface can be associated with security groups that differ from those associated with the ECS's other interfaces. Huawei Cloud explicitly states that an extended network interface created through the console can be attached to an instance in the same VPC while using different security groups.

Huawei documentation additionally specifies that when an extended network interface is created through the appropriate API, it can be attached to an instance residing in a different VPC. Therefore, the broader proposition in the question—that an ECS and an extended interface can belong to different VPCs or security groups—is technically supported by Huawei Cloud.

For conventional console-based deployments, the normal architecture places the ECS's primary and extended interfaces in different subnets of the same VPC, with security rules independently assignable to individual interfaces. This provides traffic separation for service, management, internal, and external networks. The API capability extends this flexibility further.

Consequently, because Huawei officially supports both differentiated security-group association and cross-VPC attachment under the documented API scenario, the correct answer is TRUE.

Reference topics: Elastic Network Interfaces; Extension NICs; VPC Networking; Security Group Association.

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