In an end-to-end Quality of Service (QoS) design, the goal is to maintain the priority of traffic as it transitions from the wireless medium (WMM) to the wired infrastructure (Ethernet).
WMM to DSCP Mapping: Aruba APs map Wireless MultiMedia (WMM) Access Categories (like Voice or Video) to specific DSCP (Differentiated Services Code Point) values in the IP header before forwarding the frames onto the wired network.
The Concept of " Trust " : By default, many switches operate in a " trusted " or " untrusted " mode. If a port is untrusted, the switch will strip or ignore any DSCP markings on incoming packets and remark them to 0 (Best Effort). To prevent this, the AOS-CX switch must be configured to trust the incoming DSCP markings.
Applying Trust via Interface (Option B): On the physical ports where APs are connected, you must apply the command qos trust dscp. This ensures that as the AP sends traffic into the switch, the switch honors the DSCP values assigned by the AP.
Applying Trust via User-Role (Option A): In modern Aruba " Colorless Port " architectures, switches often use User-Based Tunneling (UBT) or local roles assigned via ClearPass. If the AP itself is assigned a " User-Role " upon connection, that role can include a QoS policy that specifies DSCP trust. This is the preferred method for dynamic environments because the security and QoS policies follow the device regardless of which physical port it uses.
Why other options are incorrect:
Option C: LLDP-MED is used to negotiate parameters (like Voice VLAN), but it doesn ' t provide the granular " trust " mechanism required for WMM-to-DSCP mapping.
Option D: Colorless ports are a deployment method for roles, but " Colorless ports " is not a configuration command that handles QoS prioritization itself.
Option E: AOS-CX does not typically utilize a " global " trust command; trust is applied at the ingress point (interface or role) to maintain security and control.
