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IntermediatePublished 2026-06-25

Port Membership & Trunking: VLAN Assignment + Verification

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Hands-on CCNA VLAN and trunking lab: assign access ports by interface range, build and harden 802.1Q trunks, set a dedicated native VLAN, correct a misassigned user port, and verify VLAN membership. Includes a cross-switch path with a router-on-a-stick gateway, tests from real hosts, and troubleshooting of trunk allow-lists and native VLAN mismatches.

Track
Est. time
70 minutes
Difficulty
Intermediate
Topics

Learning objectives

  • Create and name VLANs on Cisco IOS Layer-2 switches
  • Assign multiple access ports to a VLAN using interface ranges
  • Configure a hardened 802.1Q trunk with explicit allowed VLANs and a non-default native VLAN
  • Build router-on-a-stick subinterfaces for per-VLAN gateways
  • Verify VLAN membership with show vlan brief and show interfaces switchport
  • Troubleshoot reachability failures caused by misassigned access ports, missing VLANs on trunks, or native VLAN mismatch

Troubleshooting focus

  • CLIENT-USER01 cannot reach SRV-FILE01 at 10.10.10.20: read each user port with show interfaces switchport and compare its actual access VLAN against the VLAN that segment is supposed to use. Correct any mismatch and re-verify with the same command.
  • show interfaces trunk omits VLAN 10 or 99: those VLANs are missing from that trunk's allowed list. Add them on both ends — both sides must match.
  • CDP/LLDP warns of a native VLAN mismatch, or ARP behaves intermittently: one trunk end is native 99 and the other is native 1. Set native VLAN 99 explicitly on both ends.
  • A port references a VLAN that show vlan brief does not list: the VLAN was never created. Create it on the switch so it becomes active.
  • RTR-BRANCH-EDGE subinterfaces are down in show ip interface brief: the switchport facing the router must be a trunk, the encapsulation VLAN IDs must match the subinterface tags, and the router's physical interface must be no shutdown.
  • A switch's Vlan99 SVI is down/down: an SVI comes up only with an active port in that VLAN or the VLAN carried on an up trunk. Verify the trunks and VLAN 99's status.

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Learn VLANs, Trunking & Inter-VLAN RoutingWhat Is a VLAN? VLANs Explained for Beginners

Grade your work

How this lab is graded
  • Build it your way. Where a lab lets you choose a value — a VLAN name, an interface description — grading checks that you configured it, not which name you picked. Names that another line has to reference, like an ACL applied with access-class, are stated in the guide and do have to match.
  • Addresses, modes and protocol keywords are exact. An IP address, a subnet mask, switchport mode trunk, an encapsulation — these carry the meaning of the lab, so they are graded as written in the guide.
  • Grading reads your saved configuration. Export the lab from CML after you have configured it, and make sure anything you set is in the running-config — a change that only exists in a terminal session never reaches the grader.
  • You can submit as many times as you like. Your best score stands, and each attempt tells you which checks passed so you can work the gaps.
  • Scored something you believe is correct? Use Report an issue on this page — that is exactly how the grading fixes in the changelog got found.

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