CCNA Switching and Network Access Practice Test 20 — 15 Questions

Question 1

You are connected to a multilayer switch MLSW1. PortFast and BPDU Guard have already been enabled on interface GigabitEthernet0/1, which connects to an end device, and a BPDU received on that interface placed it in the err-disabled state. Configure Rapid PVST+ so that MLSW1 becomes the root bridge for VLAN 10 with a priority of 4096. Recover the interface by re-enabling it. Finally, verify which port is blocking on VLAN 10 by connecting to MLSW2 and executing the appropriate show command.

Accepted Answer

spanning-tree vlan 10 priority 4096; interface GigabitEthernet0/1; shutdown; no shutdown; show spanning-tree vlan 10. The correct solution sets the spanning-tree priority for VLAN 10 to 4096 on MLSW1, ensuring it becomes the root bridge. PortFast and BPDU Guard are already configured on G0/1, which caused the interface to go err-disabled when a BPDU was received. To recover, you must issue the 'shutdown' followed by 'no shutdown' commands on the interface. Because MLSW1 is the root bridge, it has no blocking ports; the blocking port (alternate) will be seen on a downstream switch like MLSW2. Therefore, verification must be done on MLSW2 using 'show spanning-tree vlan 10' to view the alternate blocking port. Option A correctly includes all required steps. Option B uses 'root primary' (priority 24576) instead of the specified 4096, lacks the recovery commands, and verifies on the wrong device. Option C omits the err-disabled recovery and uses the wrong verification command. Option D also verifies with 'show running-config', which does not display STP port roles.

Answer

spanning-tree vlan 10 root primary; interface GigabitEthernet0/1; no shutdown; show spanning-tree vlan 10

Answer

spanning-tree vlan 10 priority 4096; interface GigabitEthernet0/1; no shutdown; show interfaces status

Answer

spanning-tree vlan 10 priority 4096; interface GigabitEthernet0/1; shutdown; no shutdown; show running-config

Question 2

You are connected to SW1. The network has experienced a spanning-tree topology change, and the new root bridge is not the intended core switch. Configure SW1 with a root primary priority, enable PortFast and BPDU Guard on interface GigabitEthernet0/3 (an edge port connected to a server), and verify that a specific port in the topology is blocking. Then, after a BPDU violation occurs on G0/3, recover the interface from err-disable state without reloading the switch.

Accepted Answer

spanning-tree vlan 1 root primary; interface GigabitEthernet0/3; spanning-tree portfast; spanning-tree bpduguard enable; interface GigabitEthernet0/3; shutdown; no shutdown. The current root bridge has priority 32769, but the intended root should be SW1 with a lower priority. First, configure SW1 as root primary using 'spanning-tree vlan 1 root primary' or manually set priority to 24576. For edge port Gi0/3, enable PortFast with 'spanning-tree portfast' and BPDU Guard with 'spanning-tree bpduguard enable'. After the BPDU violation, the port is err-disabled. To recover, first shut down and then no shut the interface, or use 'errdisable recovery cause bpduguard' and wait for the recovery interval, but the most direct method is to manually bounce the interface.

Answer

spanning-tree vlan 1 priority 4096; interface GigabitEthernet0/3; spanning-tree portfast; spanning-tree bpduguard enable; interface GigabitEthernet0/3; errdisable recovery cause bpduguard

Answer

spanning-tree vlan 1 root secondary; interface GigabitEthernet0/3; spanning-tree portfast; spanning-tree bpduguard enable; interface GigabitEthernet0/3; no shutdown

Answer

spanning-tree vlan 1 root primary; interface GigabitEthernet0/3; spanning-tree portfast; spanning-tree bpdufilter enable; interface GigabitEthernet0/3; shutdown; no shutdown

Question 3

You are connected to a multilayer switch MLS1. The network has two other switches: SW2 and SW3. The interface GigabitEthernet0/1 already has PortFast and BPDU Guard enabled. Configure MLS1 as the root bridge for VLAN 10 and VLAN 20 using the root primary command. After configuration, verify that the interface is not in err-disabled state and that the root bridge role is correctly assigned.

Accepted Answer

Configure 'spanning-tree vlan 10 root primary' and 'spanning-tree vlan 20 root primary' on MLS1. Verify with 'show spanning-tree vlan 10' and 'show interfaces gigabitEthernet0/1 status'.. The interface Gi0/1 already has PortFast and BPDU Guard configured, so no additional configuration is needed for that step. Using 'spanning-tree vlan 10 root primary' and 'spanning-tree vlan 20 root primary' sets the priority to 24576, ensuring MLS1 becomes root for both VLANs. Verify with 'show spanning-tree vlan 10' to see the priority changed and 'show interfaces gigabitEthernet0/1 status' to confirm the port is not err-disabled.

Answer

Configure 'spanning-tree vlan 10 root primary' and 'spanning-tree vlan 20 root secondary' on MLS1. Verify with 'show spanning-tree vlan 10' and 'show interfaces gigabitEthernet0/1 status'.

Answer

Configure 'spanning-tree vlan 10 priority 4096' and 'spanning-tree vlan 20 priority 4096' on MLS1. Verify with 'show spanning-tree vlan 10' and 'show interfaces gigabitEthernet0/1 status'.

Answer

Configure 'spanning-tree vlan 10 root primary' and 'spanning-tree vlan 20 root primary' on MLS1. Then configure 'spanning-tree portfast default' and 'spanning-tree bpduguard default' globally. Verify with 'show spanning-tree vlan 10' and 'show interfaces gigabitEthernet0/1 status'.

Question 4

You are connected to R1, a multilayer switch running Rapid PVST+. The current root bridge for VLAN 10 has priority 24586 and for VLAN 20 has priority 24676. Configure R1 so that it becomes the root bridge for VLAN 10 and VLAN 20. Then enable PortFast and BPDU Guard on interface FastEthernet0/1, which connects to an access switch. Finally, diagnose why interface FastEthernet0/2 has entered an err-disabled state and recover it.

Accepted Answer

Configure spanning-tree vlan 10,20 priority 4096; on Fa0/1: spanning-tree portfast and spanning-tree bpduguard enable; on Fa0/2: shutdown then no shutdown.. To become the root bridge, R1’s priority must be lower than the current root’s priority. Setting the priority to 4096 (or any value lower than 24586/24676) accomplishes this. Option A correctly uses `spanning-tree vlan 10,20 priority 4096` (though the actual command per VLAN is `spanning-tree vlan 10 priority 4096` and `spanning-tree vlan 20 priority 4096`). It also enables PortFast and BPDU Guard on Fa0/1 to prevent BPDU reception on an edge port, and recovers the err-disabled Fa0/2 by cycling `shutdown` then `no shutdown`. Options B and C fail because they do not enable BPDU Guard, leaving the interface vulnerable. Option D fails because it only shuts down Fa0/2 without the `no shutdown` command, so the interface remains administratively down.

Answer

Configure spanning-tree vlan 10,20 root primary; on Fa0/1: spanning-tree portfast; on Fa0/2: no shutdown.

Answer

Configure spanning-tree vlan 10,20 priority 8192; on Fa0/1: spanning-tree portfast; on Fa0/2: no shutdown.

Answer

Configure spanning-tree vlan 10,20 priority 4096; on Fa0/1: spanning-tree portfast and spanning-tree bpduguard enable; on Fa0/2: shutdown.

Question 5

You are connected to SW1. The network has three switches (SW1, SW2, SW3) running Rapid-PVST+. SW1 should be the root bridge for VLAN 10. PortFast and BPDU Guard must be enabled on all edge ports connected to end hosts. An err-disabled port (G0/1) has occurred due to a BPDU violation on an edge port. Recover the port and ensure it is configured correctly to prevent recurrence.

Accepted Answer

Enter interface configuration mode for Gi0/1, issue 'shutdown' followed by 'no shutdown', then verify that the connected device is not a switch or remove it from the network.. The port Gi0/1 is in err-disabled state because BPDU Guard disabled it after receiving a BPDU on a PortFast edge port. First, shut down the interface and then re-enable it with 'no shutdown' to recover from err-disabled. However, to prevent recurrence, the root cause must be addressed: the connected device (likely another switch) should not be sending BPDUs on an edge port. Optionally, you can disable BPDU Guard on that specific port if it is not truly an edge port, but the task requires PortFast and BPDU Guard on edge ports. The correct fix is to ensure no BPDUs are sent from the downstream device or use 'spanning-tree bpduguard disable' on that port if it is not an edge port (but the task mandates BPDU Guard). Since the scenario requires BPDU Guard, the candidate should recover the port and then verify that the connected device is not a switch (or remove it from the topology).

Answer

Enter interface configuration mode for Gi0/1, issue 'shutdown' followed by 'no shutdown', then configure 'spanning-tree bpduguard disable' on the interface.

Answer

Enter interface configuration mode for Gi0/1, issue 'shutdown' followed by 'no shutdown', then configure 'spanning-tree portfast' and 'spanning-tree bpduguard enable' on the interface.

Answer

Enter interface configuration mode for Gi0/1, issue 'shutdown' followed by 'no shutdown', then configure 'spanning-tree guard root' on the interface.

Question 6

You are connected to SW1 via the console. The network has three switches connected in a triangle: SW1 (G0/1 to SW2 G0/1), SW1 (G0/2 to SW3 G0/1), and SW2 (G0/2 to SW3 G0/2). SW1 is the root bridge. A PC is connected to SW3's G0/3 port, which should be an edge port. However, the PC has been sending BPDUs, causing the port to go err-disabled. Configure SW3 to prevent this in the future: enable PortFast and BPDU Guard on G0/3. Then, verify that the port recovers from err-disabled state and that a specific blocked port on SW2 is identified. Use the provided show output to determine the current state and necessary commands.

Accepted Answer

interface g0/3
 spanning-tree portfast
 spanning-tree bpduguard enable
 shutdown
 no shutdown. The PC connected to SW3's G0/3 was sending BPDUs, causing the port to go err-disabled due to BPDU Guard. To prevent this, enable PortFast and BPDU Guard on that interface. First, move to interface configuration mode for G0/3, then issue 'spanning-tree portfast' and 'spanning-tree bpduguard enable'. After configuration, the port will remain err-disabled until manually recovered by issuing 'shutdown' followed by 'no shutdown'. The blocked port on SW2 is G0/2, as shown by the 'Altn BLK' role/status in its spanning-tree output.

Answer

interface g0/3
 spanning-tree portfast
 spanning-tree bpduguard enable
 no shutdown

Answer

interface g0/3
 spanning-tree portfast
 spanning-tree bpduguard enable
 end
 copy running-config startup-config

Answer

interface g0/3
 spanning-tree portfast
 spanning-tree bpduguard enable
 shutdown

Question 7

You are connected to switch SW1. The network uses Rapid-PVST+ and SW1 has been accidentally configured with a low spanning-tree priority, causing it to become the root bridge for VLAN 10 even though it should not be. Additionally, an edge port connected to a server is repeatedly receiving BPDUs, causing it to go into err-disabled state. Configure SW1 so that it is never the root bridge for VLAN 10, and configure the edge port so that it automatically recovers from err-disabled state after 300 seconds. Finally, verify that SW1 is not the root bridge for VLAN 10.

Accepted Answer

spanning-tree vlan 10 priority 36864; errdisable recovery cause bpduguard; errdisable recovery interval 300; show spanning-tree vlan 10. The issue is that SW1 has the spanning-tree priority for VLAN 10 set to 4096, which makes it the root bridge. To prevent this, you must set the priority higher than the current root bridge's priority (e.g., 32768 or higher). Additionally, the edge port (G0/1) is in err-disabled state because it received a BPDU while PortFast was enabled (BPDU Guard triggered). To automatically recover from err-disabled, you need to configure errdisable recovery cause bpduguard and set the interval to 300 seconds. After configuration, verify with 'show spanning-tree vlan 10' that SW1 is no longer the root and 'show errdisable recovery' to confirm the recovery settings.

Answer

spanning-tree vlan 10 priority 4096; errdisable recovery cause bpduguard; errdisable recovery interval 300; show spanning-tree vlan 10

Answer

spanning-tree vlan 10 root secondary; errdisable recovery cause bpduguard; errdisable recovery interval 300; show spanning-tree vlan 10

Answer

spanning-tree vlan 10 priority 32768; errdisable recovery cause all; errdisable recovery interval 300; show spanning-tree vlan 10

Question 8

You are connected to a multilayer switch MLS1. The network has two other switches SW1 and SW2 forming a triangle topology. Currently, SW1 is the root bridge but it should be SW2. Additionally, configure PortFast and BPDU Guard on interface GigabitEthernet0/2 of MLS1, which connects to a host. Simulate a BPDU violation on that port and then recover the port from err-disabled state.

Accepted Answer

On MLS1, remove 'spanning-tree vlan 1 root primary' and set priority to 4096; on SW2, set priority to 0. On MLS1 Gi0/2, configure 'spanning-tree portfast' and 'spanning-tree bpduguard enable'. After BPDU violation, recover with 'shutdown' then 'no shutdown'.. Currently, SW1 is the root bridge per the topology, but the goal is to make SW2 the root. On MLS1, removing the 'spanning-tree vlan 1 root primary' command and setting a higher priority (4096) ensures it does not interfere. On SW2, set priority to 0 to make it root. On MLS1 Gi0/2, configure PortFast and BPDU Guard. If a BPDU is received, the port goes err-disabled; to recover, issue 'shutdown' then 'no shutdown' after resolving the BPDU source.

Answer

On MLS1, set priority to 0 to make it root; on SW2, set priority to 4096. On MLS1 Gi0/2, configure 'spanning-tree portfast' and 'spanning-tree bpduguard enable'. After BPDU violation, recover by removing BPDU Guard.

Answer

On MLS1, remove 'spanning-tree vlan 1 root primary' and set priority to 4096; on SW2, set priority to 0. On MLS1 Gi0/2, configure 'spanning-tree portfast' and 'spanning-tree bpduguard enable'. After BPDU violation, recover by reloading MLS1.

Answer

On MLS1, set priority to 0; on SW2, set priority to 4096. On MLS1 Gi0/2, configure 'spanning-tree portfast' and 'spanning-tree bpduguard enable'. After BPDU violation, recover with 'no shutdown'.

Question 9

You are connected to switch SW1 via console. The network uses Rapid-PVST+ and you need to ensure that SW1 becomes the root bridge for VLANs 10 and 20. Additionally, configure PortFast and BPDU Guard on interface GigabitEthernet0/2, which connects to an end host. Finally, diagnose why interface GigabitEthernet0/3 is in err-disabled state and bring it back operational.

Accepted Answer

Configure SW1 with spanning-tree vlan 10,20 priority 4096, enable PortFast and BPDU Guard on Gi0/2, and recover Gi0/3 by identifying the cause and using shutdown/no shutdown.. To make SW1 the root bridge for VLANs 10 and 20, configure 'spanning-tree vlan 10,20 priority 4096' (a valid multiple of 4096). Interface Gi0/2 connects to an end host, so enable PortFast with 'spanning-tree portfast' and BPDU Guard with 'spanning-tree bpduguard enable' under the interface to protect against accidental BPDU reception. Gi0/3 is in err-disabled state. Common causes include a port-security violation, UDLD misconfiguration, or a loopback detection. To recover, identify the cause with 'show interfaces status err-disabled', then administratively shut and no shut the interface. Option A correctly accomplishes these tasks. Option B uses an invalid priority value (0) and reloading the switch is unnecessary. Option C configures 'root primary', which sets priority to 24576 but not 4096, and globally enabling PortFast and BPDU Guard is not recommended; also 'errdisable recovery cause all' might recover the port automatically but does not address the root cause. Option D uses priority 8192 (too high) and physical cable manipulation is not a valid recovery method.

Answer

Set SW1's priority to 0 for VLANs 10 and 20, enable PortFast on Gi0/2, and recover Gi0/3 by reloading the switch.

Answer

Configure SW1 with spanning-tree vlan 10,20 root primary, enable PortFast and BPDU Guard globally, and recover Gi0/3 by using the 'errdisable recovery cause all' command.

Answer

Set SW1's priority to 8192 for VLANs 10 and 20, enable PortFast on Gi0/2, and recover Gi0/3 by removing and reinserting the cable.

Question 10

You are connected to R1, a multilayer switch acting as the root bridge for VLAN 10. The network has experienced a loop, and interface GigabitEthernet0/1 on R1 is currently in err-disabled state due to a BPDU guard violation. Configure the switch to recover automatically from err-disable state after 300 seconds, then verify that the interface comes back up.

Accepted Answer

Configure 'errdisable recovery cause bpduguard' and 'errdisable recovery interval 300' globally, then verify with 'show interfaces status'.. The interface Gi0/1 is in err-disabled state because BPDU Guard detected an unexpected BPDU on a PortFast-enabled access port. To recover automatically, configure errdisable recovery cause bpduguard and set the recovery interval to 300 seconds with errdisable recovery interval 300. After applying these commands, the interface will automatically come out of err-disable state after 300 seconds. The blocking port on Gi0/2 is expected because R1 is the root bridge and Gi0/2 is an alternate port providing redundancy; no action is needed for that blocking state.

Answer

Configure 'spanning-tree portfast bpduguard default' and 'errdisable recovery interval 300' globally, then verify with 'show spanning-tree'.

Answer

Configure 'errdisable recovery cause all' and 'errdisable recovery interval 300' globally, then verify with 'show errdisable recovery'.

Answer

Configure 'errdisable recovery cause bpduguard' and 'errdisable recovery interval 300' on interface GigabitEthernet0/1, then verify with 'show interfaces GigabitEthernet0/1'.

Question 11

You are connected to switch SW1. Configure Rapid-PVST+ so that SW1 becomes the root bridge for VLAN 10 and VLAN 20. On interface GigabitEthernet0/2, enable PortFast and BPDUGuard. Then, a BPDU is received on that port, causing err-disable. Diagnose the issue and recover the interface without rebooting the switch.

Accepted Answer

Configure SW1 as root for VLAN 10 and 20 using 'spanning-tree vlan 10 root primary' and 'spanning-tree vlan 20 root primary'. On Gi0/2, enable PortFast with 'spanning-tree portfast' and BPDUGuard with 'spanning-tree bpduguard enable'. The err-disable state occurs because BPDUGuard shuts down the port when a BPDU is received. To recover, use 'errdisable recovery cause bpduguard' to enable automatic recovery, or manually do 'shutdown' followed by 'no shutdown' on the interface.. First, configure SW1 as root for VLAN 10 and 20 using 'spanning-tree vlan 10 root primary' and 'spanning-tree vlan 20 root primary'. Then, on interface Gi0/2, enable PortFast with 'spanning-tree portfast' and BPDUGuard with 'spanning-tree bpduguard enable'. The err-disable state occurs because BPDUGuard defaults to shutting down a port when a BPDU is received. To recover, use 'errdisable recovery cause bpduguard' to allow automatic recovery or 'shutdown' followed by 'no shutdown' on the interface. The blocking port is Gi0/2 in VLAN 20 because the current root has a higher priority than SW1's configured priority, but since SW1 becomes root, all ports are designated.

Answer

Configure SW1 as root for VLAN 10 and 20 using 'spanning-tree vlan 10 root primary' and 'spanning-tree vlan 20 root primary'. On Gi0/2, enable PortFast with 'spanning-tree portfast' and BPDUGuard with 'spanning-tree bpduguard enable'. The err-disable state occurs because BPDUGuard shuts down the port when a BPDU is received. To recover, use 'clear spanning-tree detected-protocols' on the interface.

Answer

Configure SW1 as root for VLAN 10 and 20 using 'spanning-tree vlan 10 root primary' and 'spanning-tree vlan 20 root primary'. On Gi0/2, enable PortFast with 'spanning-tree portfast' and BPDUGuard with 'spanning-tree bpduguard enable'. The err-disable state occurs because BPDUGuard shuts down the port when a BPDU is received. To recover, use 'no spanning-tree bpduguard enable' on the interface, then re-enable it.

Answer

Configure SW1 as root for VLAN 10 and 20 using 'spanning-tree vlan 10 root primary' and 'spanning-tree vlan 20 root primary'. On Gi0/2, enable PortFast with 'spanning-tree portfast' and BPDUGuard with 'spanning-tree bpduguard enable'. The err-disable state occurs because BPDUGuard shuts down the port when a BPDU is received. To recover, use 'reload' on the switch to reset all interfaces.

Question 12

You are connected to R1, a Catalyst 3650 multilayer switch running IOS-XE. Configure Root Guard on all designated ports, Loop Guard on uplink interfaces, and BPDU Guard on all PortFast-enabled ports. Troubleshoot the current issue: one port is receiving a superior BPDU and is being blocked by Root Guard, and a different PortFast port has gone err-disabled after BPDU Guard triggered. Verify that Root Guard is active on port Gi1/0/1, Loop Guard is active on Gi1/0/2, and BPDU Guard is enabled on Gi1/0/3.

Accepted Answer

Remove Root Guard from Gi1/0/1 and apply it to Gi1/0/2; remove Loop Guard from Gi1/0/2 and apply it to Gi1/0/1; on Gi1/0/3, issue shutdown then no shutdown; verify Root Guard on Gi1/0/2, Loop Guard on Gi1/0/1, BPDU Guard on Gi1/0/3.. The network requires Root Guard on designated ports, Loop Guard on uplink (root/alternate) ports, and BPDU Guard on PortFast ports. Gi1/0/1 is receiving a superior BPDU and being blocked by Root Guard, indicating Root Guard is misapplied to a non-designated port; it should be moved to the designated port Gi1/0/2. Loop Guard belongs on the uplink port Gi1/0/1, not Gi1/0/2, so the configuration is swapped. The PortFast port Gi1/0/3 experienced a BPDU Guard violation and is err-disabled; recovering it requires a shutdown followed by a no shutdown command, not just no shutdown. Finally, verification must confirm the correct new placement: Root Guard on Gi1/0/2, Loop Guard on Gi1/0/1, and BPDU Guard on Gi1/0/3.

Answer

Remove Root Guard from Gi1/0/1 and apply it to Gi1/0/2; remove Loop Guard from Gi1/0/2 and apply it to Gi1/0/1; on Gi1/0/3, issue no shutdown; verify Root Guard on Gi1/0/2, Loop Guard on Gi1/0/1, BPDU Guard on Gi1/0/3.

Answer

Remove Root Guard from Gi1/0/1 and apply it to Gi1/0/2; remove Loop Guard from Gi1/0/2 and apply it to Gi1/0/1; on Gi1/0/3, issue shutdown then no shutdown; verify Root Guard on Gi1/0/1, Loop Guard on Gi1/0/2, BPDU Guard on Gi1/0/3.

Answer

Remove Root Guard from Gi1/0/1 and apply it to Gi1/0/2; remove Loop Guard from Gi1/0/2 and apply it to Gi1/0/1; on Gi1/0/3, issue shutdown then no shutdown; verify Root Guard on Gi1/0/2, Loop Guard on Gi1/0/2, BPDU Guard on Gi1/0/3.

Question 13

You are connected to R1, a multilayer switch with three directly connected switches. Configure Root Guard on the designated port to prevent an unauthorized switch from becoming root. Configure Loop Guard on the uplink to protect against unidirectional links. Configure BPDU Guard on all PortFast-enabled ports. Troubleshoot the scenario where a port receives a superior BPDU and is blocked by Root Guard, and another port goes err-disabled after BPDU Guard triggers.

Accepted Answer

Configure Root Guard on Gi0/2, Loop Guard on Gi0/2, and BPDU Guard on Gi0/1 and Gi0/3.. The scenario requires three STP protection features. Root Guard should be applied on designated port Gi0/2 (uplink) to prevent an external switch from becoming root if it sends superior BPDUs. Loop Guard should be applied on the same uplink to protect against unidirectional link failure. BPDU Guard must be enabled on all PortFast ports (Gi0/1 and Gi0/3) to immediately err-disable them if a BPDU is received. After configuration, if a superior BPDU arrives on Gi0/2, Root Guard will block it (root-inconsistent state). If a BPDU arrives on Gi0/1 or Gi0/3, BPDU Guard will put the port in err-disable state, requiring manual or automatic recovery.

Answer

Configure Root Guard on Gi0/1 and Gi0/3, Loop Guard on Gi0/2, and BPDU Guard on Gi0/2.

Answer

Configure Root Guard on Gi0/1, Loop Guard on Gi0/3, and BPDU Guard on Gi0/2.

Answer

Configure Root Guard on Gi0/3, Loop Guard on Gi0/1, and BPDU Guard on Gi0/2.

Question 14

You are connected to R1, a multilayer switch acting as the STP root for VLAN 10. Configure Root Guard on port GigabitEthernet0/1 (designated port) to protect against superior BPDUs from an unauthorized switch, Loop Guard on uplink GigabitEthernet0/2 to prevent loops, and BPDU Guard on PortFast-enabled GigabitEthernet0/3. After configuration, a superior BPDU arrives on G0/1, blocking the port; verify the Root Guard state and ensure BPDU Guard triggers err-disable on G0/3.

Accepted Answer

G0/1 is in root-inconsistent state; G0/3 is in err-disabled state.. Root Guard is needed on the designated port (G0/1) to prevent an unauthorized switch from becoming root by sending superior BPDUs. Loop Guard on the uplink (G0/2) prevents loops if BPDUs stop arriving. BPDU Guard on PortFast ports (G0/3) immediately err-disables them upon BPDU reception. The configuration uses 'spanning-tree guard root' on G0/1, 'spanning-tree guard loop' on G0/2, and 'spanning-tree bpduguard enable' on G0/3. Verification shows G0/1 blocked by root-inconsistent state and G0/3 in err-disabled state.

Answer

G0/1 is in blocking state; G0/3 is in err-disabled state.

Answer

G0/1 is in root-inconsistent state; G0/3 is in blocking state.

Answer

G0/1 is in err-disabled state; G0/3 is in root-inconsistent state.

Question 15

You are connected to R1, a multilayer switch acting as the STP root bridge. Configure Root Guard on the designated port toward R2 (G0/1), Loop Guard on the uplink port G0/2, and BPDU Guard on PortFast-enabled access port G0/3. After configuration, a superior BPDU is received on G0/1, causing it to be blocked by Root Guard; later, an unauthorized BPDU on G0/3 triggers err-disable. Troubleshoot and verify the expected port states.

Accepted Answer

G0/1 is in blocking state (Root Guard), G0/2 is in forwarding state (Loop Guard), G0/3 is in err-disable state (BPDU Guard).. The root guard on G0/1 correctly blocked the port when a superior BPDU was received, preventing an unauthorized root bridge. Loop Guard was applied specifically to the uplink port G0/2 to prevent forwarding loops in case of uni-directional link failure. BPDU Guard on G0/3 placed the port into err-disable state upon receiving an unexpected BPDU, which protects the PortFast edge port. To restore G0/3, you must manually shut/no shut the interface after removing the offending device.

Answer

G0/1 is in forwarding state (Root Guard), G0/2 is in blocking state (Loop Guard), G0/3 is in err-disable state (BPDU Guard).

Answer

G0/1 is in err-disable state (Root Guard), G0/2 is in forwarding state (Loop Guard), G0/3 is in blocking state (BPDU Guard).

Answer

G0/1 is in blocking state (Root Guard), G0/2 is in loop-inconsistent state (Loop Guard), G0/3 is in err-disable state (BPDU Guard).

CCNA Switching and Network Access Practice Test 20 — 15 Questions

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CCNA Switching and Network Access Practice Test 20 — 15 Questions

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