CCNA Switching and Network Access Practice Test 6 — 15 Questions

Question 1

You are connected to R1. The network consists of R1, a router, and SW1, a Layer 2 switch. VLANs 10 (192.168.10.0/24) and 20 (192.168.20.0/24) are configured on SW1 with hosts in each VLAN. R1 must perform inter-VLAN routing using a router-on-a-stick configuration on interface G0/0. Currently, hosts in VLAN 10 cannot ping hosts in VLAN 20. Configure R1 and identify and resolve the issue.

Accepted Answer

Ensure the trunk between R1 and SW1 is configured with 'switchport trunk allowed vlan 10,20' on SW1.. In a router-on-a-stick configuration, R1 must have subinterfaces with dot1Q encapsulation and IP addresses for each VLAN, and the switch port connecting to R1 must be configured as a trunk that allows VLANs 10 and 20. The 'ip routing' command is not required on a router because routing is enabled by default. Since the stem indicates VLANs are configured on SW1 and hosts cannot ping across VLANs, the most likely missing piece is the trunk allowed VLAN configuration on SW1, making option C the correct resolution.

Answer

Enable IP routing on R1 with the 'ip routing' global configuration command.

Answer

Configure the physical interface G0/0 with an IP address and enable trunking with 'switchport mode trunk'.

Answer

Add the 'no shutdown' command on R1's subinterfaces G0/0.10 and G0/0.20.

Question 2

You are connected to R1. The network uses a router-on-a-stick design with a single switch (SW1) and two VLANs: VLAN 10 (10.0.10.0/24) and VLAN 20 (10.0.20.0/24). The current configuration has connectivity issues: PCs in VLAN 20 cannot ping the router interface or each other, and there is a native VLAN mismatch on the trunk. Configure R1 to correct the native VLAN mismatch, ensure the trunk allows both VLANs, enable inter-VLAN routing, and fix any subinterface encapsulation errors so that all PCs can reach the router and each other across VLANs.

Accepted Answer

interface gig0/0.10
encapsulation dot1Q 10
ip address 10.0.10.1 255.255.255.0
interface gig0/0.20
encapsulation dot1Q 20
ip address 10.0.20.1 255.255.255.0. The correct configuration for a router-on-a-stick topology. Routers do not support switchport commands; instead, they use subinterfaces with encapsulation dot1q to route between VLANs. Option B configures subinterfaces for VLAN 10 and 20 with the correct encapsulation and IP addresses. The missing 'ip routing' command is typically enabled by default on Cisco routers, but if not, it must be added separately to enable inter-VLAN routing. Option A is invalid because it attempts to use switchport commands on a router interface. Option C incorrectly sets native VLAN to 1 and uses switchport commands. Option D disables IP routing, preventing inter-VLAN routing.

Answer

interface gig0/0
no shutdown
switchport trunk native vlan 99
switchport trunk allowed vlan 10,20
ip routing

Answer

interface gig0/0
no shutdown
switchport trunk native vlan 1
switchport trunk allowed vlan 10,20
ip routing

Answer

interface gig0/0
no shutdown
switchport trunk native vlan 99
switchport trunk allowed vlan 10,20
no ip routing

Question 3

You are connected to R1. The network consists of R1, SW1, and two VLANs (10 and 20). SW1 has hosts in VLAN 10 and VLAN 20 connected to its access ports. Configure R1 for router-on-a-stick inter-VLAN routing using subinterfaces on G0/0. The physical interface G0/0 is administratively up (no shutdown). The current configuration is incomplete and has errors preventing communication between the VLANs. Fix the configuration so that hosts in VLAN 10 (192.168.10.0/24) and VLAN 20 (192.168.20.0/24) can ping each other through R1.

Accepted Answer

Enable IP routing with the 'ip routing' global configuration command.. On Cisco routers, IPv4 routing is enabled by default; the 'ip routing' global command is only required on multilayer switches. The physical interface is already administratively up, so 'no shutdown' is unnecessary. The correct fix would be to ensure subinterfaces G0/0.10 and G0/0.20 have 'encapsulation dot1Q 10' and 'encapsulation dot1Q 20' respectively, with matching IP addresses for VLANs 10 and 20. None of the given options correctly resolve the issue.

Answer

Change the encapsulation on subinterface G0/0.10 to dot1Q 20 and on G0/0.20 to dot1Q 10.

Answer

Add the 'no shutdown' command on the physical interface G0/0.

Answer

Configure the native VLAN on the trunk to match the subinterface for VLAN 1.

Question 4

You are connected to R1. Configure router-on-a-stick inter-VLAN routing so that hosts in VLAN 10 and VLAN 20 can communicate through R1. The switch (not shown) is already configured with the correct VLANs and trunk. Troubleshoot and fix any issues in the current R1 configuration.

Accepted Answer

Enable IP routing globally and bring up the main interface GigabitEthernet0/0 with 'no shutdown'.. The R1 configuration has two subinterfaces (G0/0.10 and G0/0.20) with correct VLAN encapsulation and IP addresses, but inter-VLAN routing fails because the main interface G0/0 is administratively down (needs 'no shutdown') and IPv4 routing is disabled globally (needs 'ip routing' if not already enabled). Once the physical interface is up and routing is enabled, the subinterfaces will route between VLANs.

Answer

Change the encapsulation on the subinterfaces to 'encapsulation dot1Q 10 native' and 'encapsulation dot1Q 20 native'.

Answer

Remove the subinterfaces and configure IP addresses directly on GigabitEthernet0/0.

Answer

Add 'ip routing' on each subinterface individually.

Question 5

You are connected to R1. Configure R1 and SW1 so that hosts in VLAN 10 (192.168.10.0/24) and VLAN 20 (192.168.20.0/24) can communicate via the router-on-a-stick setup. The current configuration has errors: the trunk port between SW1 and R1 has a native VLAN mismatch, VLAN 30 is not allowed on the trunk, and the subinterface encapsulation is incorrect. Correct these issues and enable inter-VLAN routing.

Accepted Answer

On R1, configure interface GigabitEthernet0/0.30 with encapsulation dot1Q 99 native; on SW1, allow VLAN 30 on the trunk interface.. The native VLAN on SW1 is 99, while R1's physical interface defaults to native VLAN 1, causing a mismatch. To fix this, configure subinterface Gi0/0.30 on R1 with encapsulation dot1Q 99 native, making R1's native VLAN 99, matching SW1. Additionally, VLAN 30 is currently not allowed on the trunk between SW1 and R1 (the trunk only permits VLANs 10 and 20); this must be corrected by adding VLAN 30 to the trunk's allowed list. After these changes, the trunk will properly carry all required VLANs, and inter-VLAN routing between VLAN 10 and VLAN 20 will function correctly.

Answer

On R1, configure interface GigabitEthernet0/0.30 with encapsulation dot1Q 30; on SW1, remove VLAN 30 from the trunk allowed list.

Answer

On R1, configure interface GigabitEthernet0/0.30 with encapsulation dot1Q 30; on SW1, set the native VLAN to 1 on the trunk.

Answer

On R1, configure interface GigabitEthernet0/0.30 with encapsulation dot1Q 30; on SW1, configure the trunk to allow only VLANs 10 and 20.

Question 6

You are troubleshooting inter-VLAN routing on a router-on-a-stick setup. R1 is connected to SW1 via trunk port G0/0. VLANs 10, 20, and 30 exist on SW1, and R1 should route between them. Currently, hosts in VLAN 10 can communicate with VLAN 20 but cannot reach VLAN 30. Review the provided configuration and fix the issue.

R1 configuration:
interface GigabitEthernet0/0
 no shutdown
interface GigabitEthernet0/0.10
 encapsulation dot1Q 10
 ip address 192.168.10.1 255.255.255.0
interface GigabitEthernet0/0.20
 encapsulation dot1Q 20
 ip address 192.168.20.1 255.255.255.0
interface GigabitEthernet0/0.30
 encapsulation dot1Q 100
 ip address 192.168.30.1 255.255.255.0

SW1 configuration:
interface GigabitEthernet0/1
 switchport trunk encapsulation dot1q
 switchport mode trunk
 switchport trunk allowed vlan 10,20,30

Accepted Answer

Change the encapsulation on subinterface G0/0.30 to dot1Q 30 and reapply the IP address.. The subinterface for VLAN 30 (G0/0.30) is misconfigured with encapsulation dot1Q 100 instead of dot1Q 30, so R1 cannot forward packets to VLAN 30. VLAN 20 is correctly set up, which is why VLAN 10-to-VLAN 20 pings succeed. Changing the encapsulation to dot1Q 30 and reapplying the IP address restores full inter-VLAN routing. IP routing is enabled by default, so no additional command is needed; the native VLAN does not require a subinterface because no hosts are in that VLAN.

Answer

Add a subinterface for native VLAN 1 on R1 and assign an IP address.

Answer

Enable IP routing on R1 with the 'ip routing' command.

Answer

Change the allowed VLAN list on the trunk to include VLAN 30.

Question 7

You are connected to R1 via console. R1 is a router-on-a-stick connecting VLAN 10 and VLAN 20 on a single link to switch SW1. Currently, hosts in VLAN 10 cannot ping hosts in VLAN 20, and some VLAN 10 hosts report intermittent connectivity. Examine the provided configuration and output, then fix all issues to restore full inter-VLAN routing and stable trunk operation.

Accepted Answer

On R1, configure 'ip routing', add subinterface G0/0.99 with 'encapsulation dot1Q 99 native' and an IP address, and ensure G0/0 is not shutdown.. Three issues contribute to the problem. First, the router may be missing the global 'ip routing' command (if it was disabled), which prevents inter-VLAN routing. Second, the physical interface G0/0 may be administratively down; it must be enabled with 'no shutdown'. Third, the trunk's native VLAN is VLAN 99, and the router lacks a subinterface to handle untagged native VLAN traffic. The subinterface G0/0.99 with 'encapsulation dot1Q 99 native' allows the router to process untagged frames sent on the native VLAN, which is required for stable trunk operation (e.g., CDP, management) and to avoid misinterpreting untagged frames. Option A correctly enables routing, brings up the interface, and adds the native VLAN subinterface. The other options are incorrect: they either misconfigure the native encapsulation on non-native subinterfaces or attempt to use the physical interface IP for routing, which is not appropriate in a router-on-a-stick design.

Answer

On R1, configure 'ip routing' and change the encapsulation on the VLAN 10 subinterface to 'encapsulation dot1Q 10 native'.

Answer

On R1, configure 'ip routing' and add an IP address to the physical interface GigabitEthernet0/0.

Answer

On R1, configure 'ip routing' and change the encapsulation on the VLAN 20 subinterface to 'encapsulation dot1Q 20 native'.

Question 8

You are connected to R1. The network has two VLANs (10 and 20) on SW1, connected to R1 via a trunk. Currently, hosts in VLAN 10 cannot reach the router or each other across VLANs. Configure R1 with the correct subinterface encapsulation and IP addressing, and ensure the trunk on SW1 allows both VLANs. Also, fix any native VLAN mismatch on the trunk link. Which configuration steps will resolve the issues?

Accepted Answer

On R1, configure subinterface Gi0/0.10 with encapsulation dot1Q 10 native and IP 192.168.10.1/24, and subinterface Gi0/0.20 with encapsulation dot1Q 20 and IP 192.168.20.1/24. Enable ip routing. On SW1, set native VLAN to 10 on trunk Gi0/1.. For router-on-a-stick, R1 needs one subinterface per user VLAN: Gi0/0.10 with encapsulation dot1Q 10 and 192.168.10.1/24, and Gi0/0.20 with encapsulation dot1Q 20 and 192.168.20.1/24, plus 'ip routing' for inter-VLAN forwarding. If the switch trunk uses native VLAN 10, untagged VLAN 10 frames arrive on R1, so the VLAN 10 subinterface must use 'encapsulation dot1Q 10 native'. Option D matches that and leaves VLAN 20 as tagged. Option A/C configure only VLAN 1, and Option B uses 'dot1Q 10' without 'native' while the switch sends VLAN 10 untagged, causing a native-VLAN mismatch.

Answer

On R1, configure subinterface Gi0/0.1 with encapsulation dot1Q 1 native and IP 192.168.1.1/24, and enable ip routing. On SW1, ensure trunk Gi0/1 allows VLANs 10,20 and set native VLAN 1.

Answer

On R1, configure subinterface Gi0/0.10 with encapsulation dot1Q 10 and IP 192.168.10.1/24, and subinterface Gi0/0.20 with encapsulation dot1Q 20 and IP 192.168.20.1/24. Enable ip routing. On SW1, change native VLAN to 10 on trunk Gi0/1.

Answer

On R1, configure subinterface Gi0/0.1 with encapsulation dot1Q 1 (without native keyword) and IP 192.168.1.1/24. Enable ip routing. On SW1, ensure trunk Gi0/1 allows VLANs 10,20 and set native VLAN 1.

Question 9

You are connected to a multilayer switch MLS1. Configure it so that IP phones connected to FastEthernet 0/1 and FastEthernet 0/2 use voice VLAN 20 and receive power via PoE. Additionally, FastEthernet 0/3 must be configured as an access port for a wireless access point (AP) on VLAN 30, with PoE enabled. Verify your configuration using 'show interfaces switchport' and 'show power inline'.

Accepted Answer

Configure 'switchport voice vlan 20' on Fa0/1 and Fa0/2; configure Fa0/3 as an access port on VLAN 30; ensure PoE is enabled (auto) on all three ports.. To meet the requirements, Fa0/1 and Fa0/2 need 'switchport voice vlan 20', and Fa0/3 needs 'switchport mode access' and 'switchport access vlan 30'. PoE must be enabled with 'power inline auto' on all three ports. Option A includes the required voice VLAN on Fa0/1 and Fa0/2, the access VLAN on Fa0/3, and PoE on all three ports, so it is correct.

Answer

Configure 'switchport mode trunk' on Fa0/1 and Fa0/2, and set the native VLAN to 20; enable PoE on Fa0/3.

Answer

Configure 'switchport access vlan 20' on Fa0/1 and Fa0/2, and 'switchport voice vlan 30' on Fa0/3; enable PoE globally.

Answer

Configure 'power inline never' on Fa0/1 and Fa0/2, and 'switchport voice vlan 20' on Fa0/3; ensure Fa0/3 is in trunk mode.

Question 10

You are connected to SW1. This is a Layer 2 switch that connects multiple IP phones and an AP. The AP is on Gi0/3 and must receive PoE and be placed in VLAN 100 (native VLAN). IP phones on Gi0/1 and Gi0/2 must use VLAN 20 for voice and VLAN 10 for data, and must receive PoE. Currently, the AP cannot get an IP address and the phones have no voice connectivity. Configure SW1 to fix these issues.

Accepted Answer

interface Gi0/1; switchport voice vlan 20; power inline auto; interface Gi0/2; switchport voice vlan 20; power inline auto; interface Gi0/3; power inline auto. The AP on Gi0/3 already has the correct VLAN assignment (access VLAN 100 as per the requirement). The only missing piece is PoE, which is provided by 'power inline auto'. The IP phones on Gi0/1 and Gi0/2 already have data VLAN 10 configured (as shown in the initial configs), but they lack the voice VLAN (VLAN 20) and PoE. Option A adds the necessary voice VLAN and PoE to both phone ports, and adds PoE to the AP port. This resolves the issues: the AP gets an IP address (since it is now powered and in VLAN 100), and the phones can now use VLAN 20 for voice. Option B incorrectly sets the voice VLAN to 10 instead of 20. Option C fails to enable PoE on the AP port, so the AP remains unpowered. Option D does not configure voice VLANs and attempts to apply trunk native VLAN 100 to all ports, which is incorrect for access ports. Therefore, Option A is correct.

Answer

interface Gi0/1; switchport voice vlan 10; power inline auto; interface Gi0/2; switchport voice vlan 10; power inline auto; interface Gi0/3; switchport access vlan 100; power inline auto

Answer

interface Gi0/1; switchport voice vlan 20; interface Gi0/2; switchport voice vlan 20; interface Gi0/3; switchport access vlan 100

Answer

interface Gi0/1; power inline auto; interface Gi0/2; power inline auto; interface Gi0/3; power inline auto; switchport trunk native vlan 100

Question 11

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 for VLAN 10 and VLAN 20, R1's priority must be lower than the current root priorities (24586 and 24676). Setting the priority to 4096 (or any value less than 24586/24676) achieves this. Although the command in option A uses combined syntax ('spanning-tree vlan 10,20 priority 4096'), the required Cisco IOS commands are separate: 'spanning-tree vlan 10 priority 4096' and 'spanning-tree vlan 20 priority 4096'. Option A also correctly enables PortFast and BPDU Guard on FastEthernet0/1 to secure the edge port, and recovers the err-disabled interface FastEthernet0/2 with 'shutdown' followed by 'no shutdown'. Options B and C fail because they do not enable BPDU Guard (required for the scenario). Option D fails because it only issues 'shutdown' without 'no shutdown', leaving the interface 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 12

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 port-security violation, UDLD misconfiguration, or loopback detection. To recover, identify the cause with 'show interfaces status err-disabled', take corrective action, then administratively shut and no shut the interface. Option A correctly accomplishes these tasks. Option B is incomplete because it omits BPDU Guard and reloading the switch is unnecessary; priority 0 is a valid priority value, so that is not the issue. Option C configures PortFast and BPDU Guard globally rather than on Gi0/2, and 'errdisable recovery cause all' does not diagnose the root cause; 'root primary' is a valid way to become root, but not the reason C is wrong. Option D uses priority 8192, which does not guarantee root, omits BPDU Guard, 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 13

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 mode rapid-pvst', '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, enable Rapid PVST+ globally with 'spanning-tree mode rapid-pvst'. Then configure SW1 as root for VLAN 10 and 20 using 'spanning-tree vlan 10 root primary' and 'spanning-tree vlan 20 root primary'. 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.

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 14

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 explanation states that Root Guard should be applied on designated port Gi0/2, and then incorrectly states that Loop Guard should be applied on the *same* uplink. Loop Guard is designed for root or alternate ports (ports that receive BPDUs) to protect against unidirectional link failures, preventing them from transitioning to forwarding if BPDUs stop arriving. It is not typically applied to designated ports (ports that send BPDUs). Therefore, applying both Root Guard (for designated ports) and Loop Guard (for root/alternate ports) on the same port is a technical contradiction. Consequently, the marked correct option A is incorrect.

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 15

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 forwarding loops on unidirectional links, and BPDU Guard on PortFast-enabled GigabitEthernet0/3 to shut down the port if a BPDU is received. After configuration, troubleshoot the scenario: a superior BPDU is received on G0/1, causing it to be blocked by Root Guard, and an unauthorized switch sends a BPDU to G0/3, placing it in err-disable state. Verify the final configuration and state.

Accepted Answer

Root Guard on G0/1 is correctly configured; when a superior BPDU is received, the port is placed into a root-inconsistent state (BKN* in show spanning-tree) to prevent the switch from becoming root. Loop Guard on G0/2 prevents loops if BPDUs stop arriving due to a unidirectional link. BPDU Guard on G0/3, combined with PortFast, err-disables the port upon receiving any BPDU, as shown by the err-disabled status. To recover, the administrator must manually re-enable the interface after removing the offending device. No additional configuration is required; the existing commands are correct and produce the expected behavior.. The scenario demonstrates three STP protection mechanisms. Root Guard on G0/1 is correctly configured; when a superior BPDU is received, the port is placed into a root-inconsistent state (BKN* in show spanning-tree) to prevent the switch from becoming root. Loop Guard on G0/2 prevents loops if BPDUs stop arriving due to a unidirectional link. BPDU Guard on G0/3, combined with PortFast, err-disables the port upon receiving any BPDU, as shown by the err-disabled status. To recover, the administrator must manually re-enable the interface after removing the offending device. No additional configuration is required; the existing commands are correct and produce the expected behavior.

Answer

Root Guard on G0/1 is incorrectly configured; it should be configured on the root port, not the designated port. Loop Guard on G0/2 is correctly configured. BPDU Guard on G0/3 is correctly configured, but the port should automatically recover from err-disable state after a timeout.

Answer

Root Guard on G0/1 is correctly configured. Loop Guard on G0/2 is incorrectly configured because Loop Guard should be applied to root ports, not uplink ports. BPDU Guard on G0/3 is correctly configured, but the port should be in a blocking state, not err-disabled.

Answer

Root Guard on G0/1 is correctly configured. Loop Guard on G0/2 is correctly configured. BPDU Guard on G0/3 is incorrectly configured because BPDU Guard should be applied to trunk ports, not access ports, and the port should be placed in a root-inconsistent state.

CCNA Switching and Network Access Practice Test 6 — 15 Questions

Exhibit

CCNA Switching and Network Access Practice Test 6 — 15 Questions

Exhibit