200-301 Question #1785: Real Exam Question with Answer & Explanation

Question

SIMULATION 74 Please use the "Tasks" and "Topology" tabs to complete this lablet. Topology Tasks Complete the tasks below: Task 1 Configure 802.1q trunks between Sw1 and Sw2 on ports E0/0 and E0/1. - Only permit VLANs 10 and 30 on the trunks. Task 2 Using LACP, create a Port Channel between Sw1 and Sw2. - Combine E0/0 and E0/1 into a Port Channel while leaving the trunk configurations intact. - Assign number 10. - Both links must negotiate. Answer: Configure LACP EtherChannel (Po10) and keep 802.1Q trunk allowing only VLANs 10 and 30 (do on both SW1 and SW2): conf t interface range e0/0-1 switchport trunk encapsulation dot1q switchport mode trunk switchport trunk allowed vlan 10,30 channel-group 10 mode active exit interface port-channel 10 switchport trunk encapsulation dot1q switchport mode trunk switchport trunk allowed vlan 10,30 mode trunk + allowed vlan 10,30 builds the required 802.1Q trunk and restricts VLANs. channel-group 10 mode active uses LACP and ensures both links negotiate (active/active). Applying trunk settings on Po10 preserves the trunk behavior once the bundle forms.

Explanation

This simulation tests the ability to configure 802.1Q trunking restricted to specific VLANs and then bundle two trunk links into an LACP EtherChannel (Port Channel) on Cisco IOS switches. Both tasks must coexist: the EtherChannel inherits trunk settings from member interfaces and the Port Channel interface itself must also be configured as a trunk.

Approach. First, 'switchport trunk encapsulation dot1q' sets the correct frame tagging standard (required on IOS switches before setting trunk mode). 'switchport mode trunk' forces the port into unconditional trunking, and 'switchport trunk allowed vlan 10,30' restricts the trunk to only the required VLANs. 'channel-group 10 mode active' places both physical ports into Port Channel 10 using LACP in active mode — active/active on both ends guarantees negotiation as required. Finally, the Port Channel 10 logical interface must have the same trunk encapsulation and allowed VLAN settings applied independently, because the port-channel interface is treated as its own Layer 2 entity and does not automatically inherit all settings from the member ports.

Concept tested. EtherChannel (LACP / 802.3ad) combined with 802.1Q trunking: configuring LACP mode active on both physical member ports, assigning them to a numbered Port Channel, and ensuring trunk encapsulation and VLAN pruning are consistently applied to both the physical interfaces and the logical Port Channel interface.

Reference. Cisco IOS LAN Switching Configuration Guide — EtherChannel and 802.1Q Trunking; CCNA 200-301 Exam Topic 2.3 (EtherChannel) and 2.2 (Inter-VLAN routing / trunking)

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