In OpenStack, Keystone is the Identity service responsible for authentication and authorization. A core Keystone concept is that permissions are not usually granted directly to a user; instead, users are assigned one or more roles, and those roles are associated with a project, domain, or system scope. OpenStack’s official Keystone documentation states that the Identity service assigns roles to users, and a user can have different roles in different projects. It also explains that default roles such as admin, member, and reader are used to control what actions a user can perform. This means the statement is correct: Keystone users are assigned roles, and those roles determine their permissions.

This is also consistent with Huawei Cloud’s identity and permission model, where permissions are controlled through assigned authorization policies and identities use tokens containing identity and permission information when accessing services. In practical Huawei Cloud Stack and OpenStack-based environments, role-based access control is the standard method for defining what a user is allowed to do. Therefore, the correct answer is TRUE .

The correct answer is B. BMS . For a typical web application architecture on HUAWEI CLOUD Stack, ECS provides the compute instances, IMS provides reusable images for quick deployment, AS enables elastic scale-out and scale-in based on demand, and ELB distributes traffic and improves availability. Huawei’s ECS and IMS documentation explicitly notes that ECS images can be used with Auto Scaling for dynamic expansion to meet peak demand, which directly supports quick deployment and elasticity.

BMS is a dedicated bare-metal service intended for scenarios needing direct physical hardware access, stronger isolation, or reduced virtualization overhead. It is useful for special workloads, but it is not required for the classic goals listed in the question, especially high cost-effectiveness and fast elastic web scaling. Those goals are more naturally achieved with ECS-based architectures plus ELB and AS. Huawei’s BMS positioning emphasizes physical-server management and performance advantages, not being a necessary part of a standard web application elasticity stack. Therefore, among the listed services, the one that is not required is BMS , making B the verified answer.

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The correct answer is B. VM performance deteriorates. Huawei’s official Resource Audit Overview for HUAWEI CLOUD Stack explains that Service OM resource audit is designed for high-frequency exception types caused by unplanned system failures, such as host reboot, process restart, or backup recovery. Huawei explicitly states that resource audit is used when problems such as residual resources and unavailable resources occur after those events. This directly matches options C and D. The same audit section also covers scenarios like abnormal VM states, orphan VMs, fake VMs, and image or volume inconsistencies caused by restoration or failed processes.

By contrast, VM performance deterioration is a performance management or capacity tuning issue, not a resource-audit exception type. Huawei’s compute resource management materials discuss performance tuning separately, such as changing VM flavors or adjusting resources, which shows that performance degradation is not handled by the Service OM resource-audit function itself. Therefore, among the four options, the issue that cannot be handled by Service OM’s resource audit is B.

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The correct answer is C. Quick and elastic adjustment of CPUs and memory . Huawei’s official HUAWEI CLOUD Stack materials describe Bare Metal Server (BMS) as dedicated physical servers that provide excellent or remarkable computing performance and direct access to physical resources. Huawei also explains that Ironic works with Nova and Neutron to manage BMS resources, highlighting the physical-server nature of the service. These characteristics support advantages such as physical isolation , no hypervisor performance overhead , and direct access to specialized hardware .

By contrast, Huawei’s ECS Advantages documentation explicitly says that with ECS, administrators can modify an ECS flavor, including the number of CPUs and memory size . That kind of quick and elastic CPU/memory adjustment is therefore an ECS advantage , not a BMS-over-ECS advantage.

So after correcting the option formatting, A , B , and D are all real BMS strengths, while C belongs more to virtualized ECS elasticity. Therefore, the verified answer is C .

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The statement is FALSE . Official OpenStack Heat documentation says that when the Orchestration service was originally introduced, it worked with AWS CloudFormation templates , which are in JSON format. It then states that Heat also runs HOT templates written in YAML . This directly disproves the claim that both HOT and CFN templates support YAML in the same native sense.

OpenStack Heat documentation also explains that HOT was introduced to replace the Heat CloudFormation-compatible format (CFN) as the native format supported by Heat over time. That means HOT, not CFN, is the format more suitable for OpenStack-native deployments. The documentation further notes that YAML is easier to write, parse, and maintain, which is one reason HOT became the preferred OpenStack format.

Although internal parsing code shows the API can accept a JSON- or YAML-formatted document in some contexts, the OpenStack-native orchestration model clearly favors HOT and identifies CFN as the older CloudFormation-compatible format. So the combined statement is incorrect, and the correct answer is B (FALSE) .

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OpenStack is widely recognized for its openness, flexibility, and scalability . Official OpenStack documentation describes OpenStack as an open-source cloud platform that allows organizations to integrate different technologies and build clouds with a high degree of flexibility. It also explicitly highlights horizontal scalability , meaning compute, storage, and network resources can be expanded as demand grows. In addition, OpenStack and related OpenInfra materials consistently emphasize openness as a defining characteristic of the platform.

By contrast, efficiency is certainly a benefit that cloud platforms may deliver, but it is not typically presented as one of the foundational core concepts of OpenStack in the same way as openness, flexibility, and scalability. Huawei-authored OpenStack content also discusses OpenStack in terms of openness and scalability, which aligns with the standard industry description rather than listing efficiency as a core concept. Therefore, among the options given, Efficiency is the one that is not considered a core concept of OpenStack.

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The best verified answer is A, B, and D . Huawei networking documentation shows that Internet access troubleshooting for cloud resources commonly involves checking whether an EIP is bound or whether a NAT gateway is configured , which supports A . Huawei guidance also explicitly refers to selecting or checking an appropriate EIP bandwidth , which supports D as a normal troubleshooting item.

Huawei documentation also shows that network ACL rules are part of VPC access control and can affect connectivity. Because network ACLs are stateless and traffic validation depends on rule direction, checking ACL rules is a reasonable O & M troubleshooting operation. In your option wording, inbound rules are still part of that validation scope, so B is acceptable.

By contrast, checking route configurations on core switches is not the standard first-line troubleshooting action for tenant-side VPC Internet access in Huawei Cloud Stack service O & M. The cloud service boundary is usually diagnosed first through NAT, ACL, and EIP-related configuration. Therefore, the verified answer is A, B, and D .

The correct answer is B. L3 Agent . Official OpenStack Neutron documentation states that routers provide virtual Layer 3 services such as routing and NAT , and that the Networking service uses a layer-3 agent to manage routers. OpenStack also explicitly says that the neutron-l3-agent uses the Linux IP stack and iptables to perform L3 forwarding and NAT . This directly matches the wording of the question.

The other options do not fit. The L2 agent handles local virtual switch configuration and Layer 2 networking behavior, not routing and NAT. The DHCP agent provides DHCP services to tenant networks. “ NAT Agent ” is not the standard Neutron component name used in official OpenStack architecture. OpenStack documentation consistently identifies the L3 agent as the component responsible for router namespace management, forwarding, floating IP behavior, and source NAT functions.

This is also consistent with Huawei Cloud Stack networking architecture topics, where routing and NAT functions are tied to Neutron Layer 3 services. Therefore, the fully verified answer is B. L3 Agent .