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That option concerns RSTP port roles and rapid convergence. That follows from the targeted action: Validate physical stack links, member roles and split-brain safeguards before considering a multi-switch logical chassis redundant.

That option concerns RSTP designated root and backup topology selection. That follows from the targeted action: Validate physical stack links, member roles and split-brain safeguards before considering a multi-switch logical chassis redundant.

That option concerns BFD rapid session detection and routing protocol association. That follows from the targeted action: Validate physical stack links, member roles and split-brain safeguards before considering a multi-switch logical chassis redundant.

This option proposes: Troubleshoot BGP establishment by distinguishing TCP port 179 transport, peer configuration and OPEN capability negotiation. It addresses the different topic BGP transport reachability and session states, not the directly tested Switch stacking clustering and split-brain risk failure in the stated incident (A campus stack loses its inter-member link during maintenance and both sides appear to claim active control-plane roles, threatening duplicate gateway behavior.).

This option proposes: Inspect bridge IDs, selected root bridge, root-path costs, each port role and current alternate/discarding state. It addresses the different topic RSTP port roles and rapid convergence, not the directly tested Switch stacking clustering and split-brain risk failure in the stated incident (A campus stack loses its inter-member link during maintenance and both sides appear to claim active control-plane roles, threatening duplicate gateway behavior.).

This option proposes: Trace an enterprise wireless AP's registration to its access controller and the separation of management from user traffic in supported forwarding modes. It addresses the different topic Large campus WLAN AC AP and CAPWAP architecture, not the directly tested Switch stacking clustering and split-brain risk failure in the stated incident (A campus stack loses its inter-member link during maintenance and both sides appear to claim active control-plane roles, threatening duplicate gateway behavior.).

This option proposes: Select and verify a suitable root bridge for a switched domain without relying on arbitrary port names or traffic volume. It addresses the different topic RSTP designated root and backup topology selection, not the directly tested Switch stacking clustering and split-brain risk failure in the stated incident (A technician replaces a stack member but neglects its configured stack ID and software compatibility, and the logical device cannot form.).

This option proposes: Diagnose RSTP forwarding state by identifying root, designated and alternate ports and the topology's point-to-point characteristics. It addresses the different topic RSTP port roles and rapid convergence, not the directly tested Switch stacking clustering and split-brain risk failure in the stated incident (A technician replaces a stack member but neglects its configured stack ID and software compatibility, and the logical device cannot form.).

This option proposes: Diagnose firewall traffic by checking stateful session records and security-zone policy rather than treating every permitted ACL packet as an established connection. It addresses the different topic Stateful firewall sessions versus basic packet ACL filtering, not the directly tested Switch stacking clustering and split-brain risk failure in the stated incident (A technician replaces a stack member but neglects its configured stack ID and software compatibility, and the logical device cannot form.).

This option proposes: STP and RSTP root election depends on bridge IDs and configured priorities, while root-path cost and port IDs help select forwarding roles; a device with more physical connections is not automatically elected root. It addresses the different topic RSTP designated root and backup topology selection, not the directly tested Switch stacking clustering and split-brain risk failure in the stated incident (A technician replaces a stack member but neglects its configured stack ID and software compatibility, and the logical device cannot form.).

This option proposes: MSTP can map multiple VLANs to different spanning-tree instances and balance paths, but mismatched region parameters place devices in different regions or create a boundary rather than one shared instance. It addresses the different topic MSTP region and VLAN-to-instance mappings, not the directly tested Switch stacking clustering and split-brain risk failure in the stated incident (A technician replaces a stack member but neglects its configured stack ID and software compatibility, and the logical device cannot form.).

This option proposes: MQC policy operation separates traffic classifiers, traffic behaviors and policies that bind them on a supported interface and direction; defining a classifier by itself does not apply a traffic action. It addresses the different topic Huawei MQC traffic classification and behavior binding, not the directly tested Switch stacking clustering and split-brain risk failure in the stated incident (A technician replaces a stack member but neglects its configured stack ID and software compatibility, and the logical device cannot form.).

This option proposes: Compare bridge priority and MAC-derived IDs, root bridge identity, root-path costs and per-port selection on adjacent switches. It addresses the different topic RSTP designated root and backup topology selection, not the directly tested Switch stacking clustering and split-brain risk failure in the stated incident (A technician replaces a stack member but neglects its configured stack ID and software compatibility, and the logical device cannot form.).

This option proposes: Compare MST region name, revision, VLAN-instance tables, region digest and root bridge per instance on neighboring switches. It addresses the different topic MSTP region and VLAN-to-instance mappings, not the directly tested Switch stacking clustering and split-brain risk failure in the stated incident (A technician replaces a stack member but neglects its configured stack ID and software compatibility, and the logical device cannot form.).

This option proposes: Review phase 1/IKE negotiation logs, IPsec child SA proposals, traffic selectors, encap/decap packet counters and the route to the remote subnet. It addresses the different topic IPsec VPN IKE negotiation versus ESP data channel, not the directly tested Switch stacking clustering and split-brain risk failure in the stated incident (A technician replaces a stack member but neglects its configured stack ID and software compatibility, and the logical device cannot form.).

This option proposes: Internal routers prefer the intended egress path while the preference stays within the correct autonomous system boundary. It addresses the different topic BGP LOCAL_PREF within one autonomous system, not the directly tested Switch stacking clustering and split-brain risk failure in the stated incident (A technician replaces a stack member but neglects its configured stack ID and software compatibility, and the logical device cannot form.). The better discriminating check for this case is: Inspect member and master status, stack-link connectivity, dual-active detection mechanisms and forwarding after an isolated partition test. The targeted correction is: Validate physical stack links, member roles and split-brain safeguards before considering a multi-switch logical chassis redundant.

That option concerns RSTP port roles and rapid convergence. That follows from the targeted Recommended action: Validate physical stack links, member roles and split-brain safeguards before considering a multi-switch logical chassis redundant.

That option concerns RSTP designated root and backup topology selection. That follows from the targeted Recommended action: Validate physical stack links, member roles and split-brain safeguards before considering a multi-switch logical chassis redundant.

This option proposes: Compare MST region name, revision, VLAN-instance tables, region digest and root bridge per instance on neighboring switches. It addresses the different topic MSTP region and VLAN-to-instance mappings, not the directly tested Switch stacking clustering and split-brain risk failure in the stated incident (A technician replaces a stack member but neglects its configured stack ID and software compatibility, and the logical device cannot form.). The better discriminating check for this case is: Inspect member and master status, stack-link connectivity, dual-active detection mechanisms and forwarding after an isolated partition test.

This option proposes: Trace source or destination address translation separately from security policy when applications fail across a routed perimeter. It addresses the different topic Huawei firewall NAT and address translation context, not the directly tested Switch stacking clustering and split-brain risk failure in the stated incident (A technician replaces a stack member but neglects its configured stack ID and software compatibility, and the logical device cannot form.).

This option proposes: Review broadcast-network designated-router election based on interface priority and router ID, noting that a stable election does not automatically preempt. It addresses the different topic OSPF broadcast DR and BDR election, not the directly tested Switch stacking clustering and split-brain risk failure in the stated incident (A technician replaces a stack member but neglects its configured stack ID and software compatibility, and the logical device cannot form.).

This option proposes: Trace ACL rule matching and interface direction before broadening a security filter that drops legitimate traffic. It addresses the different topic ACL traffic filter placement and rule order, not the directly tested Multicast reverse path forwarding checks failure in the stated incident (A live classroom video flow reaches a distribution router on a secondary link, but the RPF route points at a different primary uplink and the stream is dropped.).

This option proposes: Separate any-source group subscriptions from IGMPv3 source-specific multicast membership when implementing an SSM service. It addresses the different topic IGMPv3 source-specific selection and SSM, not the directly tested Multicast reverse path forwarding checks failure in the stated incident (A live classroom video flow reaches a distribution router on a secondary link, but the RPF route points at a different primary uplink and the stream is dropped.).

This option proposes: Check IGMP membership and querier operation on the receiver LAN before changing PIM routing configuration upstream. It addresses the different topic IGMP querier membership reports and group timeout, not the directly tested Multicast reverse path forwarding checks failure in the stated incident (A live classroom video flow reaches a distribution router on a secondary link, but the RPF route points at a different primary uplink and the stream is dropped.).

This option proposes: PIM-DM generally follows a flood-and-prune model, building source-based multicast distribution where an interface without interested downstream receivers can be pruned to reduce unnecessary traffic. It addresses the different topic PIM dense mode flooding and prune mechanisms, not the directly tested Multicast reverse path forwarding checks failure in the stated incident (A live classroom video flow reaches a distribution router on a secondary link, but the RPF route points at a different primary uplink and the stream is dropped.).

This option proposes: A stateful firewall tracks valid connection context and can permit related return traffic based on session state; network ACLs may filter packets independently without the same stateful application tracking. It addresses the different topic Stateful firewall sessions versus basic packet ACL filtering, not the directly tested Multicast reverse path forwarding checks failure in the stated incident (A live classroom video flow reaches a distribution router on a secondary link, but the RPF route points at a different primary uplink and the stream is dropped.).

This option proposes: In any-source PIM-SM an RP supports initial shared-tree joining and source registration, while routers may switch to source-rooted shortest-path trees according to configured behavior and traffic. It addresses the different topic PIM sparse mode RP shared tree and shortest path transition, not the directly tested Multicast reverse path forwarding checks failure in the stated incident (A live classroom video flow reaches a distribution router on a secondary link, but the RPF route points at a different primary uplink and the stream is dropped.).

This option proposes: Compare WLAN service templates, VLAN pool membership and assignment method, gateway/SVI, relay configuration and per-VLAN available leases. It addresses the different topic WLAN VLAN pools and DHCP address scopes, not the directly tested Multicast reverse path forwarding checks failure in the stated incident (A live classroom video flow reaches a distribution router on a secondary link, but the RPF route points at a different primary uplink and the stream is dropped.).

This option proposes: Compare RP reachability, (*,G) and (S,G) state, PIM join or register messages and RPF interfaces before changing the multicast design. It addresses the different topic PIM sparse mode RP shared tree and shortest path transition, not the directly tested Multicast reverse path forwarding checks failure in the stated incident (A live classroom video flow reaches a distribution router on a secondary link, but the RPF route points at a different primary uplink and the stream is dropped.).

This option proposes: Review VLAN IGMP query source, version, group reports, membership timers and the downstream interface in multicast routing state. It addresses the different topic IGMP querier membership reports and group timeout, not the directly tested Multicast reverse path forwarding checks failure in the stated incident (A live classroom video flow reaches a distribution router on a secondary link, but the RPF route points at a different primary uplink and the stream is dropped.).

That option concerns IGMP querier membership reports and group timeout. That follows from the targeted action: Diagnose a multicast drop by checking reverse path forwarding against the packet's source rather than only validating the destination group.

That option concerns IP prefix filtering and exact route-match conditions. That follows from the targeted action: Diagnose a multicast drop by checking reverse path forwarding against the packet's source rather than only validating the destination group.

That option concerns IGMPv3 source-specific selection and SSM. That follows from the targeted action: Diagnose a multicast drop by checking reverse path forwarding against the packet's source rather than only validating the destination group.