Broadcast-domain separation
VLANs create distinct logical L2 broadcast domains over shared switch hardware. ARP broadcast in VLAN 10 does not reach VLAN 20 through ordinary switching. Assign IP subnets consistently with the VLAN plan; changing a mask to make addresses look similar does not join separate VLANs.
Access, trunk and tagging
An access port normally assigns untagged endpoint traffic to one VLAN. A trunk can carry several VLANs using 802.1Q tags, subject to an allowed list and platform-specific native VLAN behavior. Both ends need compatible configuration. A VLAN existing in a switch database does not prove it is permitted across an uplink.
Inter-VLAN routing
A router subinterface or layer-3 switch interface provides a gateway for each segment. Routing and policy control traffic between them. Verify source gateway, destination route, return route and firewall permissions. Do not assume a trunk routes packets just because it carries several VLANs.
AV cross-reference
AV endpoints may need correct VLAN discovery and consistent transport paths. Segmentation must consider controller reachability, timing and multicast requirements of the real deployment. ITAV’s Dante and AV model is simplified; a functioning teaching subscription is not proof of full production protocol behavior.
Signal / protocol flow
- 1PC VLAN 10
- 2Access switch
- 3802.1Q trunk VLAN 10
- 4Remote access VLAN 10
- 5PC
Technical terminology
- Access VLAN: endpoint membership
- 802.1Q: VLAN tag format
- Trunk: multi-VLAN link
- SVI: switched virtual interface
Worked example
PC-A and PC-B have 192.168.10.10/24 and .20/24 but ports are VLAN 10 and 20. ARP cannot traverse the separation. Align the intended access VLAN or create a deliberately routed design with distinct subnets.
Configuration reference
! Cisco IOS-style reference only; not executed by ITAV vlan 10 name USERS interface GigabitEthernet1/0/1 switchport mode access switchport access vlan 10 interface GigabitEthernet1/0/24 switchport mode trunk switchport trunk allowed vlan 10,20
Troubleshooting scenario
Both access ports are correct, but uplink permits only VLAN 20. Inspect allowed lists on both ends, add the intended VLAN with a platform-safe command, then test local ARP and end-to-end service.
Knowledge check
What does a trunk allowed list control?
Related practice
References
Educational model — not real hardware, traffic or official certification.