LEARN. PRACTICE. GROW.Concept and mechanism
An installed forwarding table chooses the most specific destination match. For 10.60.8.70, /24 wins over /16 when both routes are usable. Comparing protocols to install a route is a separate decision. On switches, a VLAN must exist and be carried where required. A trunk allowing only 10,20,30 does not carry VLAN 80 merely because it exists at both ends. Also confirm port modes and tagging consistency. STP may keep a redundant path from forwarding data to prevent loops. Do not disable protection merely because a link is not forwarding; validate intended topology and distinguish aggregated links from separate paths.
Guided application
Installation includes capacity and compatibility. A switch with 90 W available cannot reserve 18 W for six simultaneous APs: that needs 108 W. Per-port limits and aggregate budget are different constraints. With fiber, mechanically compatible connectors do not guarantee a valid optical pair; compare datasheets, fiber, reach, wavelengths, and polarity. In Wi-Fi, strong signal does not mean sufficient capacity. Measure airtime utilization, interference, and retransmissions before changing power or channels. Record assumptions and measurements in handover so APS can repeat diagnosis. A trunk change should preserve existing VLANs and have rollback criteria and enough time to execute them.
Before fund close, VLAN 120 disappears from the allowed list: a limited correction may restore service without replacing the entire list.
Common pitfalls
Preferring a less specific route; creating a VLAN without checking trunks; disabling STP; miscalculating PoE; judging Wi-Fi only by signal.
Related topics: Operations, services, and recovery · Security, segmentation, and remote access
Validate addressing, L2 transport, and installation as distinct conditions of the same service.
Reference: VLAN trunks · N10-009 V9