Lab Simulation 18 Guidelines This is a lab item in which tasks will be performed on virtual devices. - Refer to the Tasks tab to view the tasks for this lab item. - Refer to the Topology tab to access

Question

Exhibits

Explanation

The lab simulation requires configuring VLAN trunking with a specific native VLAN and LACP-based EtherChannel between three Cisco switches according to detailed specifications.

Approach. The correct approach involves accessing the console of each switch (SW-1, SW-2, and SW-3) and applying the specified Cisco IOS commands to fulfill each task. The order of operations is important, especially when configuring EtherChannel, as the trunking parameters are typically applied to the Port-Channel interface.

SW-1 Configuration:

enable
configure terminal
interface range e0/0, e0/1
 channel-group 12 mode active
 exit
interface port-channel 12
 switchport trunk encapsulation dot1q
 switchport mode trunk
 switchport trunk native vlan 35
 exit
interface e0/2
 switchport trunk encapsulation dot1q
 switchport mode trunk
 switchport trunk native vlan 35
 exit
end
write memory

SW-2 Configuration:

enable
configure terminal
interface range e0/0, e0/1
 channel-group 12 mode passive
 exit
interface port-channel 12
 switchport trunk encapsulation dot1q
 switchport mode trunk
 switchport trunk native vlan 35
 exit
interface e0/2
 switchport trunk encapsulation dot1q
 switchport mode trunk
 switchport trunk native vlan 35
 exit
end
write memory

SW-3 Configuration:

enable
configure terminal
interface range e0/0, e0/1
 switchport trunk encapsulation dot1q
 switchport mode trunk
 switchport trunk native vlan 35
 exit
end
write memory

Reasoning for each task:

1. Trunking on SW-1/SW-2 e0/0 and e0/1 (Port-Channel 12): These interfaces form an EtherChannel, so trunking properties (switchport trunk encapsulation dot1q and switchport mode trunk) are applied to the logical interface port-channel 12. This allows all VLANs to pass over the trunk as per the default behavior unless switchport trunk allowed vlan is used to filter.
2. Native VLAN 35 on all inter-switch links: The command switchport trunk native vlan 35 must be applied to interface port-channel 12 (on both SW-1 and SW-2) and to the direct inter-switch links (e0/2 on SW-1, e0/2 on SW-2, and e0/0, e0/1 on SW-3). All these links must also be explicitly configured as 802.1q trunks (switchport trunk encapsulation dot1q and switchport mode trunk) for the native VLAN command to take effect.
3. LACP Link Aggregation on SW-1/SW-2 e0/0 and e0/1: On SW-1, the physical interfaces e0/0 and e0/1 are configured with channel-group 12 mode active to initiate LACP negotiation. On SW-2, the same physical interfaces are configured with channel-group 12 mode passive to respond to LACP requests, fulfilling the requirement for immediate negotiation from SW-1 and passive response from SW-2.

Common mistakes.

• common_mistake. Common mistakes include:

• Incorrect LACP modes: Setting both ends to 'passive' would prevent the EtherChannel from forming, as neither side would initiate LACP. Setting both to 'active' would work but does not meet the specific requirement that SW-2 only responds. Using 'on' mode (unconditional EtherChannel) would disable LACP and prevent dynamic negotiation.
• Forgetting to configure trunking/native VLAN on Port-Channel: Trunking parameters (switchport mode trunk, switchport trunk encapsulation dot1q, switchport trunk native vlan) must be applied to the interface port-channel 12 after the physical interfaces have been assigned to it. Applying them only to the physical interfaces before the channel group command might lead to unexpected behavior or loss of configuration.
• Missing trunk configuration on direct links: Interfaces e0/2 on SW-1, e0/2 on SW-2, and e0/0/e0/1 on SW-3 are also inter-switch links and must be configured as 802.1Q trunks with native VLAN 35. Forgetting this would result in incorrect VLAN routing between switches and SW-3.
• Incorrect encapsulation: On Cisco switches, it's crucial to specify switchport trunk encapsulation dot1q before switchport mode trunk when dealing with older switches that might support ISL, or just for best practice and clarity, even if 802.1Q is the only option.
• Not saving the configuration: Failing to execute write memory or copy running-config startup-config would result in the loss of all configurations upon reboot or lab termination.

Concept tested. The core concepts tested are Cisco IOS switch configuration for:

1. VLAN Trunking (IEEE 802.1Q): Establishing inter-switch links capable of carrying traffic for multiple VLANs.
2. Native VLAN: Understanding and configuring the untagged VLAN on 802.1Q trunks.
3. Link Aggregation (EtherChannel/Port Aggregation Protocol): Grouping multiple physical links into a single logical link for increased bandwidth and redundancy.
4. Link Aggregation Control Protocol (LACP): Dynamically negotiating EtherChannel links using active and passive modes.
5. Interface Configuration: Applying settings to physical and logical (Port-Channel) interfaces, including using interface ranges.

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