Problematic wireless adapters

A running list of wireless adapters that misbehave with Fluxion, what the symptom looks like, and what (if anything) can be done about it. Most entries here are not Fluxion bugs — they are driver/firmware limitations that show up as confusing Fluxion behavior (empty client lists, no handshake, etc.).

If you hit a similar problem, check here first. To add an adapter, copy the template at the bottom and fill it in with what you observed.

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Fenvi AX1800 (USB) — MediaTek MT7921AU / mt7921u

• Chipset: MediaTek MT7921AU (USB ID 0e8d:7961)
• Driver: mt7921u (mt76)
• Roles affected: client scanning and handshake capture (anything that relies on airodump-ng listing associated stations). Transmit roles (deauth jammer) are not affected.

Symptom

In monitor mode the adapter sees access points fine (beacons show up in airodump-ng), but the STATION list stays empty — even when clients are associated and actively passing traffic. In Fluxion this surfaces as the Captive Portal / Handshake Snooper client scanner reporting no associated clients on a target that clearly has them.

Root cause

In monitor mode the MT7921U firmware only delivers management and group-addressed (broadcast/multicast) frames to the host. It drops all unicast data frames and all control frames (ACK / Block-ACK). airodump-ng identifies a station from unicast/uplink frames and correctly refuses to attribute a group-addressed frame to a specific client, so no station is ever recorded. The real client MACs are only present as the source field (addr3) of relayed broadcast frames, which is not a valid association signal.

Ruled out (so you don’t repeat the dig)

All of the following were tested and are not the cause:

• airodump-ng version — reproduced on the packaged 1.7 and on a from-source build of git master (aircrack-ng rev 2f393ae).
• Channel hopping — interface was locked to the target BSSID/channel.
• The -a “filter unassociated clients” flag — empty with and without it.
• Channel width — identical result at HT20 and at matching HT40.
• Idle clients — clients were actively passing traffic (verified with a second host hammering the target’s Wi-Fi IP).
• A wedged firmware state — a full USB detach/replug and fresh firmware re-init behaved identically.

Confirmation: instrumenting airodump-ng’s dump_add_packet() showed every data frame arriving FromDS with a broadcast/multicast destination. A raw 15 s tcpdump across all nearby APs captured 0 control frames and 0 unicast data frames — physically impossible on a live band unless the adapter is filtering them below userspace.

Notes

• Also observed on this hardware: a mac80211 WARNING in ieee80211_recalc_offload firing on interface bring-up (kernel 7.1.5+kali). Likely a separate driver/mac80211 issue; not the direct cause of the missing stations.

Workaround

Use a different adapter for the scanning / capture role — one whose mac80211 monitor mode passes unicast and control frames, e.g. Realtek RTL8821AU, Atheros ath9k / ath9k_htc, or MediaTek mt76x2u (MT7612U). The MT7921U can stay in the deauth-jammer role, since transmit works fine. This pairs naturally with --jammer-interface / --ap-interface for multi-adapter setups.

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Template for new entries

## <Adapter name> — <Chipset> / `<driver>`

- **Chipset:** <chipset> (USB/PCI ID `xxxx:yyyy`)
- **Driver:** `<driver>`
- **Roles affected:** <scan / capture / AP / deauth>

### Symptom
<what the user sees in Fluxion / airodump>

### Root cause
<driver/firmware behavior, if known>

### Ruled out
<things tested that are NOT the cause>

### Workaround
<how to work around it, e.g. use another adapter for a given role>