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That option concerns Route redistribution feedback loops and route tags. That follows from the targeted action: Ensure consistent MST region name, revision and VLAN-to-instance mapping before expecting switches to share the same spanning-tree instance topology.

That option concerns Switch stacking clustering and split-brain risk. That follows from the targeted action: Ensure consistent MST region name, revision and VLAN-to-instance mapping before expecting switches to share the same spanning-tree instance topology.

That option concerns RSTP port roles and rapid convergence. That follows from the targeted action: Ensure consistent MST region name, revision and VLAN-to-instance mapping before expecting switches to share the same spanning-tree instance topology.

This option proposes: Disable spanning tree on every redundant uplink after seeing an alternate port discard frames, treating the loop-prevention state as a fault. It addresses the different topic RSTP port roles and rapid convergence, not the directly tested MSTP region and VLAN-to-instance mappings failure in the stated incident (Campus access switches were configured with identical MST region names but different VLAN mappings, creating a boundary where the designer expected one region.).

This option proposes: Override all AS loop checks because a longer AS_PATH is said to be universally more attractive to every external BGP neighbor. It addresses the different topic BGP AS_PATH path-vector loop prevention, not the directly tested MSTP region and VLAN-to-instance mappings failure in the stated incident (Campus access switches were configured with identical MST region names but different VLAN mappings, creating a boundary where the designer expected one region.).

This option proposes: Assume the switch with the fastest interface always becomes the spanning-tree root even when a lower bridge ID exists elsewhere. It addresses the different topic RSTP designated root and backup topology selection, not the directly tested MSTP region and VLAN-to-instance mappings failure in the stated incident (Campus access switches were configured with identical MST region names but different VLAN mappings, creating a boundary where the designer expected one region.).

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 MSTP region and VLAN-to-instance mappings failure in the stated incident (A network team wants voice VLANs to follow one distribution root and user VLANs another, but all VLANs were accidentally mapped to the same MST instance.).

This option proposes: Validate physical stack links, member roles and split-brain safeguards before considering a multi-switch logical chassis redundant. It addresses the different topic Switch stacking clustering and split-brain risk, not the directly tested MSTP region and VLAN-to-instance mappings failure in the stated incident (A network team wants voice VLANs to follow one distribution root and user VLANs another, but all VLANs were accidentally mapped to the same MST instance.).

This option proposes: Differentiate traffic policy-based routing on a matching packet from ordinary destination-based forwarding through the best RIB route. It addresses the different topic Policy-based routing versus destination routing, not the directly tested MSTP region and VLAN-to-instance mappings failure in the stated incident (A network team wants voice VLANs to follow one distribution root and user VLANs another, but all VLANs were accidentally mapped to the same MST instance.).

This option proposes: Rapid Spanning Tree Protocol reduces convergence time by exchanging proposal/agreement information on eligible links and maintaining alternate paths, while only the root and designated forwarding ports should carry traffic in a stable tree. It addresses the different topic RSTP port roles and rapid convergence, not the directly tested MSTP region and VLAN-to-instance mappings failure in the stated incident (A network team wants voice VLANs to follow one distribution root and user VLANs another, but all VLANs were accidentally mapped to the same MST instance.).

This option proposes: IGMP reports express receiver interest in multicast groups and a querier maintains group membership state; without appropriate reports or queries a router can age out forwarding toward a segment. It addresses the different topic IGMP querier membership reports and group timeout, not the directly tested MSTP region and VLAN-to-instance mappings failure in the stated incident (A network team wants voice VLANs to follow one distribution root and user VLANs another, but all VLANs were accidentally mapped to the same MST instance.).

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 MSTP region and VLAN-to-instance mappings failure in the stated incident (A network team wants voice VLANs to follow one distribution root and user VLANs another, but all VLANs were accidentally mapped to the same MST instance.).

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 MSTP region and VLAN-to-instance mappings failure in the stated incident (A network team wants voice VLANs to follow one distribution root and user VLANs another, but all VLANs were accidentally mapped to the same MST instance.).

This option proposes: Inspect member and master status, stack-link connectivity, dual-active detection mechanisms and forwarding after an isolated partition test. It addresses the different topic Switch stacking clustering and split-brain risk, not the directly tested MSTP region and VLAN-to-instance mappings failure in the stated incident (A network team wants voice VLANs to follow one distribution root and user VLANs another, but all VLANs were accidentally mapped to the same MST instance.).

This option proposes: Compare peer state transitions, source addresses, route to the peer, TCP 179 connectivity, local/remote AS settings and notification codes. It addresses the different topic BGP transport reachability and session states, not the directly tested MSTP region and VLAN-to-instance mappings failure in the stated incident (A network team wants voice VLANs to follow one distribution root and user VLANs another, but all VLANs were accidentally mapped to the same MST instance.).

That option concerns RSTP designated root and backup topology selection. That follows from the targeted Recommended action: Ensure consistent MST region name, revision and VLAN-to-instance mapping before expecting switches to share the same spanning-tree instance topology.

That option concerns ACL traffic filter placement and rule order. That follows from the targeted Recommended action: Ensure consistent MST region name, revision and VLAN-to-instance mapping before expecting switches to share the same spanning-tree instance topology.

That option concerns Switch stacking clustering and split-brain risk. That follows from the targeted Recommended action: Ensure consistent MST region name, revision and VLAN-to-instance mapping before expecting switches to share the same spanning-tree instance topology.

This option proposes: Assume the switch with the fastest interface always becomes the spanning-tree root even when a lower bridge ID exists elsewhere. It addresses the different topic RSTP designated root and backup topology selection, not the directly tested MSTP region and VLAN-to-instance mappings failure in the stated incident (A network team wants voice VLANs to follow one distribution root and user VLANs another, but all VLANs were accidentally mapped to the same MST instance.).

This option proposes: Declare a two-switch stack fully protected against dual-active behavior simply because both chassis still have electrical power. It addresses the different topic Switch stacking clustering and split-brain risk, not the directly tested MSTP region and VLAN-to-instance mappings failure in the stated incident (A network team wants voice VLANs to follow one distribution root and user VLANs another, but all VLANs were accidentally mapped to the same MST instance.).

This option proposes: Expect an EVPN Type 2 MAC advertisement alone to make an unreachable underlay VTEP routable without any transport path. It addresses the different topic MP-BGP EVPN route types and forwarding separation, not the directly tested MSTP region and VLAN-to-instance mappings failure in the stated incident (A network team wants voice VLANs to follow one distribution root and user VLANs another, but all VLANs were accidentally mapped to the same MST instance.).

This option proposes: Ensure consistent MST region name, revision and VLAN-to-instance mapping before expecting switches to share the same spanning-tree instance topology. 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 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: 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 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: Verify BGP network origination and import-route mechanisms before expecting a prefix to be advertised. It addresses the different topic BGP route origin network and redistribution policy, 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: Rapid Spanning Tree Protocol reduces convergence time by exchanging proposal/agreement information on eligible links and maintaining alternate paths, while only the root and designated forwarding ports should carry traffic in a stable tree. 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: 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 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: 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 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: 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 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: Compare received iBGP routes to the same prefix, LOCAL_PREF values, policy application points and next-hop reachability across edge routers. 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 campus stack loses its inter-member link during maintenance and both sides appear to claim active control-plane roles, threatening duplicate gateway behavior.). 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.

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 campus stack loses its inter-member link during maintenance and both sides appear to claim active control-plane roles, threatening duplicate gateway behavior.).

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.