Lab 2: Configure VLANs and 802.1Q Trunks

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Lab 2: Configure VLANs and 802.1Q Trunks

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Lesson format9 sections1 code block1 practice itemUpdated Oct 2, 2026

Take the Lab 1 topology and add a second switch. Configure VLANs 10 (Users) and 20 (Voice) on both. Trunk the inter-switch link. Users in VLAN 10 on Switch 1 should be able to reach users in VLAN 10 on Switch 2 — but not users in VLAN 20.

#The Lab Topology#link

#Configuration Steps#link

bash

! On SW1
SW1(config)# vlan 10
SW1(config-vlan)# name Users
SW1(config-vlan)# exit
SW1(config)# vlan 20
SW1(config-vlan)# name Voice
SW1(config-vlan)# exit

SW1(config)# interface gi0/1
SW1(config-if)# switchport mode access
SW1(config-if)# switchport access vlan 10
SW1(config-if)# exit

SW1(config)# interface gi0/2
SW1(config-if)# switchport mode access
SW1(config-if)# switchport access vlan 20
SW1(config-if)# exit

SW1(config)# interface gi0/24
SW1(config-if)# description Trunk-to-SW2
SW1(config-if)# switchport mode trunk
SW1(config-if)# switchport trunk allowed vlan 10,20
SW1(config-if)# switchport trunk native vlan 99
SW1(config-if)# exit

! Repeat on SW2 with ports reversed (or same ports, just mirror the trunk config)

Configure VLANs 10 and 20 on both switches. Assign access ports. Configure the inter-switch link as a trunk with allowed VLANs 10 and 20 and native VLAN 99. Verify with `show vlan brief` and `show interfaces trunk`. Test connectivity — PC-A should ping PC-C but not PC-B.

★ 20 XPmedium

challenge BLOCK (★ 20 XP)

After configuring the trunk, PC-A can ping PC-C but PC-B cannot ping PC-D. Both VLANs are in the trunk's allowed list. What should you check?

Select your proof vectors above

#Common Mistakes#link

▪Forgetting to create the VLAN on both switches — the switch won't forward for a VLAN that doesn't exist
▪Missing `switchport mode trunk` on the inter-switch link — trunk stays as access
▪Native VLAN mismatch — CDP logs a warning but trunk still operates incorrectly
▪Using `switchport trunk allowed vlan` (replaces list) instead of `add` (extends list)

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The Lab Topology Configuration Steps Common Mistakes

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October 2, 2026

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{
  "mcpServers": {
    "vulnarex": {
      "command": "npx",
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Laboratory sanity code

Isolate active probes on matched virtual networks and keep execution streams sandboxed.

! On SW1

SW1(config)# vlan 10

SW1(config-vlan)# name Users

SW1(config-vlan)# exit

SW1(config)# vlan 20

SW1(config-vlan)# name Voice

SW1(config-vlan)# exit

SW1(config)# interface gi0/1

SW1(config-if)# switchport mode access

SW1(config-if)# switchport access vlan 10

SW1(config-if)# exit

SW1(config)# interface gi0/2

SW1(config-if)# switchport mode access

SW1(config-if)# switchport access vlan 20

SW1(config-if)# exit

SW1(config)# interface gi0/24

SW1(config-if)# description Trunk-to-SW2

SW1(config-if)# switchport mode trunk

SW1(config-if)# switchport trunk allowed vlan 10,20

SW1(config-if)# switchport trunk native vlan 99

SW1(config-if)# exit

! Repeat on SW2 with ports reversed (or same ports, just mirror the trunk config)