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ENWLSI 300-430 study materials
ENWLSI 300-430 study resources

ENWLSI 300-430: Implementing Cisco Wireless Quality of Service (QoS)

ENWLSI 300-430 · Work through your exam, one topic at a time.

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Implementing Cisco Wireless Quality of Service (QoS)

The Implementing Cisco Wireless Quality of Service (QoS) domain tests whether you can carry a marking end to end: WLAN QoS profile, WMM access categories, DSCP mapping, AVC, bandwidth contracts and the FlexConnect caveats that break naive designs.

Queues and profiles

  • Standard WLC QoS profiles: Platinum (voice, DSCP EF 46), Gold (video, AF41 34), Silver (best effort, 0) and Bronze (background, low priority; the exact DSCP is editable in the QoS map).
  • WMM defines four access categories (voice, video, best effort, background) and is mandatory for 802.11n/ac/ax - disabling WMM silently drops you to legacy rates. ACM handles call admission, U-APSD handles power save.
  • Catalyst 9800 sets QoS in the policy profile with a QoS map controlling over-the-air to wired DSCP behaviour; AireOS sets per-WLAN QoS plus optional AVC.

AVC and bandwidth

  • AVC uses NBAR2 to recognize applications at the AP (local switching) or at the controller; profile rules can mark, drop or rate-limit, and the profile must be applied to the WLAN and AVC enabled.
  • Per-WLAN average/peak bandwidth contracts and per-client limits shape traffic without touching DSCP; voice CAC (TSPEC/ACM, load-based CAC) protects call quality.

FlexConnect

  • With local switching, QoS, ACLs and AVC are enforced on the AP, not the controller. Configure QoS per WLAN on the FlexConnect AP, and decide whether to trust client DSCP or have the AP mark by profile.

Worked example

Phones mark voice EF, but a capture on the AP's switch port shows DSCP 0. Reasoning: the WLAN was left on the Silver profile, so the AP/controller rewrites every frame into best effort on the way to the wire. Move the WLAN to Platinum, then verify the client's own marking with show client detail (QoS column) and re-capture. If the client marks nothing and the WLAN is Silver, the same remarking explains the failure.

Traps that cost marks

  • WMM disabled on the WLAN, which breaks 11n/ac/ax operation and prioritization.
  • QoS profile left at Silver while expecting EF upstream.
  • Assuming controller QoS applies to FlexConnect locally switched traffic.
  • AVC profile configured but not attached to the WLAN or AVC not enabled, so no statistics or enforcement appear.