VLANs and Trunking practice questions

A network engineer is troubleshooting a connectivity issue between two switches, SW1 and SW2, connected via a trunk link. SW1 is a Cisco Catalyst 3850 running IOS-XE, and SW2 is a Cisco Catalyst 2960 running IOS. The trunk is configured as a dynamic desirable mode on SW1 and dynamic auto on SW2. The engineer notices that the trunk is not forming. What is the most likely cause?

Trap 1: SW2 does not support DTP.

Incorrect because the Catalyst 2960 supports DTP.

Trap 2: The trunk encapsulation is set to ISL on SW1.

Incorrect because the 2960 only supports 802.1Q, and if SW1 were set to ISL, the trunk would not form, but the default is 802.1Q.

Trap 3: VLAN 1 is not allowed on the trunk.

Incorrect because VLAN 1 is allowed by default, and removing it would not prevent trunk formation, only traffic.

A
The native VLAN is different on SW1 and SW2.
Correct because a native VLAN mismatch can cause DTP frames to be dropped, preventing trunk negotiation.
B
SW2 does not support DTP.
Why wrong: Incorrect because the Catalyst 2960 supports DTP.
C
The trunk encapsulation is set to ISL on SW1.
Why wrong: Incorrect because the 2960 only supports 802.1Q, and if SW1 were set to ISL, the trunk would not form, but the default is 802.1Q.
D
VLAN 1 is not allowed on the trunk.
Why wrong: Incorrect because VLAN 1 is allowed by default, and removing it would not prevent trunk formation, only traffic.

Question 2mediummultiple choice

An engineer is configuring a new access switch for a branch office. The switch must support multiple VLANs for different departments: VLAN 10 (Engineering), VLAN 20 (Sales), and VLAN 30 (Management). The uplink to the distribution switch is a trunk. The engineer wants to ensure that only the required VLANs are allowed on the trunk and that the native VLAN is changed from the default to VLAN 99 for security reasons. Which configuration commands should the engineer apply on the access switch's uplink interface?

Trap 1: switchport mode trunk; switchport trunk native vlan 99; switchport…

Incorrect because 'except' would allow all VLANs except those listed, which is the opposite of the requirement.

Trap 2: switchport mode dynamic desirable; switchport trunk native vlan 99;…

Incorrect because dynamic desirable does not guarantee a trunk; it relies on DTP negotiation.

Trap 3: switchport trunk encapsulation dot1q; switchport mode trunk;…

Incorrect because it does not restrict allowed VLANs, and encapsulation command is unnecessary.

A
switchport mode trunk; switchport trunk native vlan 99; switchport trunk allowed vlan 10,20,30
Correct because it sets the trunk, changes the native VLAN, and restricts allowed VLANs.
B
switchport mode trunk; switchport trunk native vlan 99; switchport trunk allowed vlan except 10,20,30
Why wrong: Incorrect because 'except' would allow all VLANs except those listed, which is the opposite of the requirement.
C
switchport mode dynamic desirable; switchport trunk native vlan 99; switchport trunk allowed vlan 10,20,30
Why wrong: Incorrect because dynamic desirable does not guarantee a trunk; it relies on DTP negotiation.
D
switchport trunk encapsulation dot1q; switchport mode trunk; switchport trunk native vlan 99
Why wrong: Incorrect because it does not restrict allowed VLANs, and encapsulation command is unnecessary.

Question 3hardmultiple choice

A network engineer is deploying a new server farm with multiple servers connected to a Cisco Nexus 9000 switch. Each server is dual-homed to two separate access switches for redundancy. The servers are configured with NIC teaming in active-standby mode. The engineer wants to ensure that if the active link fails, traffic continues without interruption. The access switches are connected to each other via a trunk. Which technology should the engineer implement on the access switches to prevent loops and allow both uplinks to be active?

Trap 1: Enable Spanning Tree Protocol (STP) to block one of the links to…

Incorrect because STP would block one link, reducing redundancy and not allowing both links to be active.

Trap 2: Configure an EtherChannel between the server and each access switch…

Incorrect because EtherChannel requires all links to terminate on the same switch, not two different switches.

Trap 3: Implement Virtual Switching System (VSS) on the access switches.

Incorrect because VSS is for Catalyst switches, not Nexus; vPC is the Nexus equivalent.

A
Configure a vPC domain between the two access switches and use a vPC on the server-facing ports.
Correct because vPC allows both switches to act as a single logical switch for the server, providing active-active links and redundancy.
B
Enable Spanning Tree Protocol (STP) to block one of the links to prevent loops.
Why wrong: Incorrect because STP would block one link, reducing redundancy and not allowing both links to be active.
C
Configure an EtherChannel between the server and each access switch individually.
Why wrong: Incorrect because EtherChannel requires all links to terminate on the same switch, not two different switches.
D
Implement Virtual Switching System (VSS) on the access switches.
Why wrong: Incorrect because VSS is for Catalyst switches, not Nexus; vPC is the Nexus equivalent.

Question 4mediummultiple choice

An engineer is troubleshooting a problem where a host in VLAN 20 cannot communicate with a host in VLAN 30, even though both are connected to the same access switch. The access switch is configured with VLANs 20 and 30, and the uplink to the distribution switch is a trunk that allows both VLANs. The distribution switch has SVIs for both VLANs and IP routing is enabled. The engineer verifies that the trunk is up and both VLANs are allowed. What is the most likely cause of the communication failure?

Trap 1: The trunk is not allowing VLAN 20 or VLAN 30.

Incorrect because the engineer verified the trunk allows both VLANs.

Trap 2: Spanning Tree Protocol is blocking the SVI interfaces.

Incorrect because SVIs are logical interfaces and are not affected by STP.

Trap 3: The native VLAN mismatch on the trunk is causing the issue.

Incorrect because the trunk is up, so native VLAN mismatch is not present.

A
The hosts are not configured with the correct default gateway pointing to the SVI on the distribution switch.
Correct because hosts need a default gateway to route traffic to other VLANs; if misconfigured, inter-VLAN communication fails.
B
The trunk is not allowing VLAN 20 or VLAN 30.
Why wrong: Incorrect because the engineer verified the trunk allows both VLANs.
C
Spanning Tree Protocol is blocking the SVI interfaces.
Why wrong: Incorrect because SVIs are logical interfaces and are not affected by STP.
D
The native VLAN mismatch on the trunk is causing the issue.
Why wrong: Incorrect because the trunk is up, so native VLAN mismatch is not present.

Question 5easymultiple choice

A network engineer is configuring a new Cisco Catalyst 9300 switch to connect to an existing network. The uplink to the core switch is configured as a trunk. The engineer wants to ensure that all VLANs except VLAN 1 are allowed on the trunk, and that the native VLAN is set to VLAN 999. Which configuration should the engineer apply on the uplink interface?

Trap 1: switchport mode trunk; switchport trunk native vlan 999; switchport…

Incorrect because 'remove' is used to remove VLANs from the allowed list, but the syntax is 'switchport trunk allowed vlan remove 1', which would remove VLAN 1 from the current list, but the initial list includes all VLANs, so it would work, but the command is typically used in a different context. However, the 'except' command is more direct and less error-prone.

Trap 2: switchport mode trunk; switchport trunk native vlan 999; switchport…

Incorrect because it explicitly lists VLANs 2-4094, which excludes VLAN 1, but this is not as straightforward as using 'except' and could be considered less secure if VLANs are added later.

Trap 3: switchport mode trunk; switchport trunk native vlan 999; switchport…

Incorrect because 'none' blocks all VLANs, which is not the requirement.

A
switchport mode trunk; switchport trunk native vlan 999; switchport trunk allowed vlan except 1
Correct because it sets the trunk, changes the native VLAN, and allows all VLANs except VLAN 1.
B
switchport mode trunk; switchport trunk native vlan 999; switchport trunk allowed vlan remove 1
Why wrong: Incorrect because 'remove' is used to remove VLANs from the allowed list, but the syntax is 'switchport trunk allowed vlan remove 1', which would remove VLAN 1 from the current list, but the initial list includes all VLANs, so it would work, but the command is typically used in a different context. However, the 'except' command is more direct and less error-prone.
C
switchport mode trunk; switchport trunk native vlan 999; switchport trunk allowed vlan 2-4094
Why wrong: Incorrect because it explicitly lists VLANs 2-4094, which excludes VLAN 1, but this is not as straightforward as using 'except' and could be considered less secure if VLANs are added later.
D
switchport mode trunk; switchport trunk native vlan 999; switchport trunk allowed vlan none
Why wrong: Incorrect because 'none' blocks all VLANs, which is not the requirement.

Question 6hardmultiple choice

An engineer is troubleshooting a connectivity issue between two switches, SW1 and SW2, connected via a trunk. The trunk is configured with switchport mode trunk on both sides. The engineer notices that some VLANs are not passing traffic, even though they are in the allowed list. The output of 'show interfaces trunk' on SW1 shows that VLANs 10, 20, and 30 are in the allowed list and are active. However, hosts in VLAN 30 cannot reach the distribution switch. What is the most likely cause?

Trap 1: The native VLAN is mismatched between SW1 and SW2.

Incorrect because a native VLAN mismatch would affect the native VLAN traffic, not a specific non-native VLAN.

Trap 2: VTP pruning is removing VLAN 30 from the trunk.

Incorrect because if VTP pruning were active, VLAN 30 would not appear in the allowed list on the trunk.

Trap 3: The trunk is not forming due to DTP negotiation.

Incorrect because both sides are set to trunk mode, so DTP is not needed.

A
VLAN 30 is not created in the VLAN database on SW2.
Correct because a VLAN must exist in the VLAN database on both ends of a trunk for traffic to pass.
B
The native VLAN is mismatched between SW1 and SW2.
Why wrong: Incorrect because a native VLAN mismatch would affect the native VLAN traffic, not a specific non-native VLAN.
C
VTP pruning is removing VLAN 30 from the trunk.
Why wrong: Incorrect because if VTP pruning were active, VLAN 30 would not appear in the allowed list on the trunk.
D
The trunk is not forming due to DTP negotiation.
Why wrong: Incorrect because both sides are set to trunk mode, so DTP is not needed.

Question 7easymultiple choice

A network engineer is configuring a new Cisco Catalyst switch to connect to an existing network. The uplink to the distribution switch is configured as a trunk. The engineer wants to ensure that the trunk uses 802.1Q encapsulation and that the native VLAN is set to VLAN 100. The distribution switch is a Cisco Catalyst 3850. Which configuration should the engineer apply on the uplink interface?

Trap 1: switchport trunk encapsulation dot1q; switchport mode trunk;…

Incorrect because the encapsulation command is not needed on most modern switches and may be rejected.

Trap 2: switchport mode dynamic desirable; switchport trunk native vlan 100

Incorrect because dynamic desirable does not guarantee a trunk; it relies on DTP.

Trap 3: switchport mode trunk; switchport trunk allowed vlan 100

Incorrect because this command restricts allowed VLANs to only VLAN 100, and does not set the native VLAN.

A
switchport mode trunk; switchport trunk native vlan 100
Correct because it sets the trunk and changes the native VLAN to 100.
B
switchport trunk encapsulation dot1q; switchport mode trunk; switchport trunk native vlan 100
Why wrong: Incorrect because the encapsulation command is not needed on most modern switches and may be rejected.
C
switchport mode dynamic desirable; switchport trunk native vlan 100
Why wrong: Incorrect because dynamic desirable does not guarantee a trunk; it relies on DTP.
D
switchport mode trunk; switchport trunk allowed vlan 100
Why wrong: Incorrect because this command restricts allowed VLANs to only VLAN 100, and does not set the native VLAN.

Question 8mediummultiple choice

An engineer is troubleshooting a problem where a trunk link between two Cisco switches is not passing traffic for VLAN 10, but other VLANs are working. The trunk is configured with switchport mode trunk on both sides. The engineer checks the allowed VLAN list and sees VLAN 10 is included. The native VLAN is set to 1 on both sides. What is the most likely cause?

Trap 1: VTP pruning has removed VLAN 10 from the trunk.

Incorrect because if VTP pruning were active, VLAN 10 would not be in the allowed list.

Trap 2: The native VLAN is mismatched.

Incorrect because native VLAN mismatch would affect the native VLAN, not VLAN 10.

Trap 3: Spanning Tree Protocol is blocking VLAN 10 on the trunk.

Incorrect because STP blocks entire interfaces, not individual VLANs, unless using PVST+ with a loop, which is not indicated.

A
VLAN 10 is not created in the VLAN database on one of the switches.
Correct because the VLAN must exist on both switches for traffic to pass.
B
VTP pruning has removed VLAN 10 from the trunk.
Why wrong: Incorrect because if VTP pruning were active, VLAN 10 would not be in the allowed list.
C
The native VLAN is mismatched.
Why wrong: Incorrect because native VLAN mismatch would affect the native VLAN, not VLAN 10.
D
Spanning Tree Protocol is blocking VLAN 10 on the trunk.
Why wrong: Incorrect because STP blocks entire interfaces, not individual VLANs, unless using PVST+ with a loop, which is not indicated.

Question 9hardmultiple choice

A network engineer is configuring a new Cisco Nexus 9000 switch to connect to an existing Cisco Catalyst 3850 switch. The link between them should be a trunk carrying VLANs 10, 20, and 30. The engineer configures the Nexus switch with 'switchport mode trunk' and 'switchport trunk allowed vlan 10,20,30'. However, the trunk does not come up. The Catalyst switch is configured with 'switchport mode trunk' and 'switchport trunk allowed vlan 10,20,30'. What is the most likely cause?

Trap 1: The Catalyst switch is set to dynamic auto mode.

Incorrect because the scenario states both are set to trunk mode.

Trap 2: The allowed VLAN list on the Nexus switch is missing VLAN 1.

Incorrect because VLAN 1 is not required for trunking; it is allowed by default.

Trap 3: The native VLAN is set to 999 on the Nexus switch.

Incorrect because if the native VLAN were different, the trunk would still form, but native VLAN traffic would be problematic.

A
The Nexus switch does not have the 'switchport trunk encapsulation dot1q' command configured.
Correct because some Nexus switches require explicit encapsulation configuration for trunking to work with Catalyst switches.
B
The Catalyst switch is set to dynamic auto mode.
Why wrong: Incorrect because the scenario states both are set to trunk mode.
C
The allowed VLAN list on the Nexus switch is missing VLAN 1.
Why wrong: Incorrect because VLAN 1 is not required for trunking; it is allowed by default.
D
The native VLAN is set to 999 on the Nexus switch.
Why wrong: Incorrect because if the native VLAN were different, the trunk would still form, but native VLAN traffic would be problematic.

Question 10mediummultiple choice

A network engineer runs the following command on Switch SW1:

SW1# show vlan brief

VLAN Name                             Status    Ports

---- -------------------------------- --------- ------------------------------- 1 default active Gi0/1, Gi0/2, Gi0/3 10 Sales active Gi0/4, Gi0/5 20 Engineering active Gi0/6, Gi0/7 1002 fddi-default act/unsup 1003 token-ring-default act/unsup 1004 fddinet-default act/unsup 1005 trnet-default act/unsup

Based on this output, what can be concluded?

Trap 1: All ports shown are in trunk mode.

Trunk ports would appear in 'show interfaces trunk' or be listed with 'trunk' in 'show vlan brief' (some IOS versions show trunk ports as 'trunk' in the Ports column). Here, only access ports are listed.

Trap 2: VLANs 1002-1005 are active and supported.

They are shown as 'act/unsup' meaning active but unsupported on this hardware platform.

Trap 3: VLAN 20 has no ports assigned.

VLAN 20 has Gi0/6 and Gi0/7 assigned.

A
All ports shown are in trunk mode.
Why wrong: Trunk ports would appear in 'show interfaces trunk' or be listed with 'trunk' in 'show vlan brief' (some IOS versions show trunk ports as 'trunk' in the Ports column). Here, only access ports are listed.
B
VLANs 1002-1005 are active and supported.
Why wrong: They are shown as 'act/unsup' meaning active but unsupported on this hardware platform.
C
Interfaces Gi0/1, Gi0/2, and Gi0/3 are in VLAN 1.
The output clearly lists Gi0/1, Gi0/2, Gi0/3 under VLAN 1, indicating they are access ports in that VLAN.
D
VLAN 20 has no ports assigned.
Why wrong: VLAN 20 has Gi0/6 and Gi0/7 assigned.

Question 11hardmultiple choice

A network engineer runs the following command on Switch SW1:

SW1# show interfaces trunk

Port Mode Encapsulation Status Native vlan Gi0/1 on 802.1q trunking 1 Gi0/2 on 802.1q trunking 1

Port Vlans allowed on trunk Gi0/1 1-1005 Gi0/2 1-1005

Port Vlans allowed and active in management domain Gi0/1 1,10,20 Gi0/2 1,10,20

Port Vlans in spanning tree forwarding state and not pruned Gi0/1 1,10,20 Gi0/2 1,10,20

Based on this output, what can be concluded?

Trap 1: The trunk is using ISL encapsulation.

The encapsulation is shown as 802.1q.

Trap 2: VLAN 1 is pruned from the trunk.

VLAN 1 is in the forwarding state, so it is not pruned.

Trap 3: Only VLANs 10 and 20 are forwarding traffic.

VLAN 1 is also forwarding.

A
VLANs 2-9 are allowed but not active on the trunk.
The 'allowed' list includes 1-1005, but only VLANs 1,10,20 are active; thus VLANs 2-9 are allowed but not active (not created in VLAN database).
B
The trunk is using ISL encapsulation.
Why wrong: The encapsulation is shown as 802.1q.
C
VLAN 1 is pruned from the trunk.
Why wrong: VLAN 1 is in the forwarding state, so it is not pruned.
D
Only VLANs 10 and 20 are forwarding traffic.
Why wrong: VLAN 1 is also forwarding.

Question 12mediummultiple choice

A network engineer runs the following command on Switch SW1:

SW1# show interfaces gi0/1 switchport

Name: Gi0/1

Switchport: Enabled

Administrative Mode: trunk Operational Mode: trunk Administrative Trunking Encapsulation: dot1q Operational Trunking Encapsulation: dot1q Negotiation of Trunking: On Access Mode VLAN: 1 (default) Trunking Native Mode VLAN: 1 (default) Administrative Native VLAN tagging: enabled Voice VLAN: none Administrative private-vlan host-association: none Administrative private-vlan mapping: none Administrative private-vlan trunk native VLAN: none Administrative private-vlan trunk Native VLAN tagging: enabled Administrative private-vlan trunk encapsulation: dot1q Administrative private-vlan trunk normal VLANs: none Administrative private-vlan trunk private VLANs: none Operational private-vlan: none Trunking VLANs Enabled: ALL Pruning VLANs Enabled: 2-1001 Capture Mode Disabled Capture VLANs Allowed: ALL

Based on this output, what can be concluded?

Trap 1: The interface is configured as an access port.

Administrative mode is 'trunk', not 'access'.

Trap 2: The native VLAN is tagged with 802.1Q.

Actually, native VLAN tagging is enabled, meaning the native VLAN is tagged, but the statement is ambiguous. However, the correct interpretation is that native VLAN tagging is enabled, but the question asks what can be concluded. Option B is more directly supported.

Trap 3: All VLANs except 2-1001 are pruned.

Pruning VLANs Enabled: 2-1001 means those VLANs are eligible for pruning, not that they are pruned.

A
The interface is configured as an access port.
Why wrong: Administrative mode is 'trunk', not 'access'.
B
DTP is enabled on this interface.
'Negotiation of Trunking: On' indicates DTP is enabled.
C
The native VLAN is tagged with 802.1Q.
Why wrong: Actually, native VLAN tagging is enabled, meaning the native VLAN is tagged, but the statement is ambiguous. However, the correct interpretation is that native VLAN tagging is enabled, but the question asks what can be concluded. Option B is more directly supported.
D
All VLANs except 2-1001 are pruned.
Why wrong: Pruning VLANs Enabled: 2-1001 means those VLANs are eligible for pruning, not that they are pruned.

Question 13hardmultiple choice

A network engineer runs the following command on Switch SW1:

SW1# show spanning-tree vlan 10

VLAN0010 Spanning tree enabled protocol ieee Root ID Priority 32778 Address 0011.2233.4455 This bridge is the root Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec

Bridge ID Priority 32778 (priority 32768 sys-id-ext 10) Address 0011.2233.4455 Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec Aging Time 300 sec

Interface        Role Sts Cost      Prio.Nbr Type

---------------- ---- --- --------- -------- -------------------------------- Gi0/1 Desg FWD 4 128.1 P2p Gi0/2 Desg FWD 4 128.2 P2p Gi0/3 Desg FWD 4 128.3 P2p

Based on this output, what can be concluded?

Trap 1: Gi0/2 is a root port.

Root ports appear on non-root bridges; here all ports are designated.

Trap 2: The spanning-tree mode is PVST+.

The output says 'protocol ieee' which is 802.1D (classic STP), not PVST+ (which would show 'protocol ieee' as well, but PVST+ is Cisco's implementation; however, the output does not distinguish. More importantly, the priority includes sys-id-ext, which is a PVST+ feature, but the protocol line does not say 'pvst'. The safest conclusion is that it's 802.1D with extended system ID. Option A is directly supported.

Trap 3: VLAN 10 has a forwarding delay of 30 seconds.

Forward delay is 15 seconds.

A
This switch is the root bridge for VLAN 10.
The output explicitly states 'This bridge is the root'.
B
Gi0/2 is a root port.
Why wrong: Root ports appear on non-root bridges; here all ports are designated.
C
The spanning-tree mode is PVST+.
Why wrong: The output says 'protocol ieee' which is 802.1D (classic STP), not PVST+ (which would show 'protocol ieee' as well, but PVST+ is Cisco's implementation; however, the output does not distinguish. More importantly, the priority includes sys-id-ext, which is a PVST+ feature, but the protocol line does not say 'pvst'. The safest conclusion is that it's 802.1D with extended system ID. Option A is directly supported.
D
VLAN 10 has a forwarding delay of 30 seconds.
Why wrong: Forward delay is 15 seconds.

Question 14mediummultiple choice

A network engineer runs the following command on Switch SW1:

SW1# show etherchannel summary

Flags: D - down P - bundled in port-channel I - stand-alone s - suspended H - Hot-standby (LACP only) R - Layer3 S - Layer2 U - in use N - not in use, no aggregation f - failed to allocate aggregator

M - not in use, minimum links not met u - unsuitable for bundling w - waiting to be aggregated d - default port

Number of channel-groups in use: 1 Number of aggregators: 1

Group Port-channel Protocol Ports ------+-------------+-----------+-------------------------------------------- 1 Po1(SU) LACP Gi0/1(P) Gi0/2(P) Gi0/3(D)

Based on this output, what can be concluded?

Trap 1: The EtherChannel is using PAgP.

The protocol is shown as LACP.

Trap 2: Port Gi0/3 is bundled in the channel.

Gi0/3 has flag D (down), not P (bundled).

Trap 3: The port-channel is a Layer 3 interface.

The flag 'S' indicates Layer 2.

A
The EtherChannel is using PAgP.
Why wrong: The protocol is shown as LACP.
B
Port Gi0/3 is bundled in the channel.
Why wrong: Gi0/3 has flag D (down), not P (bundled).
C
The port-channel is a Layer 3 interface.
Why wrong: The flag 'S' indicates Layer 2.
D
The EtherChannel has two active member links.
Gi0/1 and Gi0/2 are marked P (bundled), so two links are active.

Question 15hardmultiple choice

A network engineer runs the following command on Switch SW1:

SW1# show vlan id 10

VLAN ID: 10
VLAN Name: Sales
VLAN Type: Ethernet
VLAN State: active

MTU: 1500

Remote SPAN VLAN: No

Primary VLAN ID: 10

Private VLAN Type: Primary

Associated Secondary VLAN IDs: 100, 200

Based on this output, what can be concluded?

Trap 1: VLAN 10 is a community VLAN.

It is a primary VLAN, not community.

Trap 2: VLAN 10 is an isolated VLAN.

It is a primary VLAN.

Trap 3: VLAN 10 is a normal data VLAN with no private VLAN features.

The output clearly indicates private VLAN configuration.

A
VLAN 10 is a community VLAN.
Why wrong: It is a primary VLAN, not community.
B
VLAN 10 is an isolated VLAN.
Why wrong: It is a primary VLAN.
C
VLAN 10 is a primary private VLAN.
The output shows 'Private VLAN Type: Primary' and associated secondary VLANs.
D
VLAN 10 is a normal data VLAN with no private VLAN features.
Why wrong: The output clearly indicates private VLAN configuration.

Question 16mediummultiple choice

A network engineer runs the following command on Switch SW1:

SW1# show interfaces gi0/1 trunk

Port Mode Encapsulation Status Native vlan Gi0/1 desirable n-802.1q trunking 1

Port Vlans allowed on trunk Gi0/1 1-1005

Port Vlans allowed and active in management domain Gi0/1 1,10,20

Port Vlans in spanning tree forwarding state and not pruned Gi0/1 1,10,20

Based on this output, what can be concluded?

Trap 1: The interface is configured as an access port.

Mode 'desirable' indicates trunk configuration.

Trap 2: The trunk is using ISL encapsulation.

Encapsulation is n-802.1q (negotiated 802.1Q).

Trap 3: The native VLAN is 10.

Native VLAN is 1.

A
The interface is configured as an access port.
Why wrong: Mode 'desirable' indicates trunk configuration.
B
The trunk is using ISL encapsulation.
Why wrong: Encapsulation is n-802.1q (negotiated 802.1Q).
C
VLANs 2-9 are allowed but not active.
Allowed VLANs are 1-1005, but only 1,10,20 are active; thus VLANs 2-9 are allowed but not active.
D
The native VLAN is 10.
Why wrong: Native VLAN is 1.

Question 17mediummultiple choice

A network engineer runs the following command on Switch SW1:

SW1# show dtp interface gi0/1

DTP information on GigabitEthernet0/1: DTP: Enabled DTP mode: Desirable DTP negotiate: TRUE DTP status: Trunk DTP trunk status: Trunking DTP timer: 30 DTP max-age: 2 DTP encapsulation: 802.1q DTP refresh rate: Both DTP requests: 10 DTP errors: 0

Based on this output, what can be concluded?

Trap 1: The interface is in access mode.

DTP status is Trunk, not access.

Trap 2: The interface is using ISL encapsulation.

Encapsulation is 802.1q.

Trap 3: DTP is disabled on this interface.

DTP is Enabled.

A
The interface is in access mode.
Why wrong: DTP status is Trunk, not access.
B
The interface will not form a trunk unless the neighbor is set to trunk or desirable.
DTP mode desirable actively sends DTP frames to form a trunk; it can form a trunk with a neighbor set to trunk, desirable, or auto.
C
The interface is using ISL encapsulation.
Why wrong: Encapsulation is 802.1q.
D
DTP is disabled on this interface.
Why wrong: DTP is Enabled.

Question 18hardmultiple choice

A network engineer runs the following command on Switch SW1:

SW1# show interfaces gi0/1 trunk

Port Mode Encapsulation Status Native vlan Gi0/1 on 802.1q trunking 1

Port Vlans allowed on trunk Gi0/1 10,20

Port Vlans allowed and active in management domain Gi0/1 10,20

Port Vlans in spanning tree forwarding state and not pruned Gi0/1 10,20

Based on this output, what can be concluded?

Trap 1: VLAN 1 is allowed on this trunk.

The allowed list shows only 10,20; VLAN 1 is not included.

Trap 2: The trunk is using DTP dynamic desirable mode.

Mode is 'on', which is static trunking without DTP.

Trap 3: The native VLAN is 10.

Native VLAN is 1.

A
VLAN 1 is allowed on this trunk.
Why wrong: The allowed list shows only 10,20; VLAN 1 is not included.
B
The trunk is using DTP dynamic desirable mode.
Why wrong: Mode is 'on', which is static trunking without DTP.
C
Only VLANs 10 and 20 are allowed on this trunk.
The 'Vlans allowed on trunk' line explicitly shows 10,20.
D
The native VLAN is 10.
Why wrong: Native VLAN is 1.

Question 19mediummultiple choice

Given the following configuration on a Cisco IOS-XE switch:

interface GigabitEthernet0/1
 switchport mode trunk
 switchport trunk native vlan 999
 switchport trunk allowed vlan 10,20,30

What is the effect of this configuration?

Trap 1: The interface will forward traffic for all VLANs except 10, 20, and…

Incorrect. The allowed VLAN list specifies which VLANs are permitted, not denied. The native VLAN is explicitly set to 999.

Trap 2: The interface will operate as an access port in VLAN 999.

Incorrect. The command 'switchport mode trunk' makes it a trunk port, not an access port.

Trap 3: The interface will forward traffic for VLANs 10, 20, and 30, and…

Incorrect. Frames on the native VLAN are sent untagged by default.

A
The interface will forward traffic for VLANs 10, 20, and 30, and all untagged frames will be placed into VLAN 999.
Correct. The allowed VLAN list restricts traffic to those three VLANs, and the native VLAN is 999.
B
The interface will forward traffic for all VLANs except 10, 20, and 30, and the native VLAN is 1.
Why wrong: Incorrect. The allowed VLAN list specifies which VLANs are permitted, not denied. The native VLAN is explicitly set to 999.
C
The interface will operate as an access port in VLAN 999.
Why wrong: Incorrect. The command 'switchport mode trunk' makes it a trunk port, not an access port.
D
The interface will forward traffic for VLANs 10, 20, and 30, and all frames will be tagged including the native VLAN.
Why wrong: Incorrect. Frames on the native VLAN are sent untagged by default.

Question 20mediummultiple choice

Examine the following configuration snippet on a Cisco IOS switch:

interface GigabitEthernet0/2
 switchport mode access
 switchport access vlan 50
 spanning-tree portfast

Which statement is true about this interface?

Trap 1: The interface will participate in trunking and forward multiple…

Incorrect. The 'switchport mode access' command makes it an access port, not a trunk.

Trap 2: The interface will still go through listening and learning states…

Incorrect. PortFast bypasses these states.

Trap 3: The interface will only forward traffic for VLAN 1.

Incorrect. The access VLAN is set to 50, so it forwards traffic for VLAN 50.

A
The interface will immediately forward traffic without any spanning-tree delay.
Correct. PortFast enables immediate forwarding, reducing the initial delay.
B
The interface will participate in trunking and forward multiple VLANs.
Why wrong: Incorrect. The 'switchport mode access' command makes it an access port, not a trunk.
C
The interface will still go through listening and learning states before forwarding.
Why wrong: Incorrect. PortFast bypasses these states.
D
The interface will only forward traffic for VLAN 1.
Why wrong: Incorrect. The access VLAN is set to 50, so it forwards traffic for VLAN 50.