Hi all,
I am troubleshooting a MikroTik WiFi/CAPsMAN issue and would like input from people with real RouterOS WiFi experience.
The summary below is summarised by an LLM but it is really me looking for answers. Hope somebody can help me find this culprit...
Setup
• hEX S as router and WiFi CAPsMAN controller
• hAP ax S as CAPs
• Local forwarding, traffic processing on CAP
• FT enabled
• FT-over-DS enabled
• GHz fixed channel layout per AP
• AX enabled
• Steering enabled with RRM/WNM
• CAPs are version aligned
Problem
Some 5 GHz clients randomly get very low throughput, often around 10 to 15 Mbps, even with good signal and even when standing close to the AP.
The best example I have:
Same AP, same SSID, same channel, same time:
Fast Mac:
AP: AP-1 / cap-wifi1
Channel: 5200 MHz / 40 MHz
RSSI around -64 dBm
802.11ax
MCS 8
NSS 2
Client shows TX rate around 412 Mbps
MikroTik registration table shows tx-rate around 300 to 413 Mbps
Slow phone:
AP: same AP-1 / cap-wifi1
Same 5 GHz SSID
Similar signal, around -58 to -64 dBm
802.11ax
auth-type=ft-wpa2-psk
MikroTik registration table shows:
tx-rate=54.0Mbps
rx-rate=325.0Mbps to 458.8Mbps
Real throughput around 10 to 15 Mbps
So the symptom seems to be: CAP-to-client downlink rate gets stuck at 54 Mbps, while client-to-CAP rate remains high.
This is not only one phone. I have seen the low-throughput behavior on multiple devices. The phone is just the cleanest current example.
Before this setup I used TP-Link Deco consumer APs in the same house and did not have this issue.
What has already been tested or confirmed
• hEX S routing is not the bottleneck
• CPU is low during the issue
• Wired speed is fine
• A Mac on the same AP can be fast while another device is slow
• GHz is not the issue
• GHz channel plan was adjusted to reduce overlap
• FT must remain enabled because roaming is worse without it
• FT-over-DS is currently enabled and should remain enabled unless there is a specific known reason not to use it
• Steering was softened
• tx-power reduction was tested and did not fix it
• All CAPs are now version aligned
• Issue can happen even when close to the AP, so it is not just sticky-client distance behavior
• Same AP and channel can serve one client fast and another client slowly at the same time
Current 5 GHz layout
AP-1: 5180,5200
AP-2: 5180,5200
AP-3: 5540,5560
AP-4: 5500,5520
AP-5: 5220,5240
The intentional channel reuse is between APs that are physically separated.
Current 5 GHz settings summary
band=5ghz-ax
width=20/40mhz
WPA2-PSK
ft=yes
ft-over-ds=yes
connect-priority=0/1
rrm=yes
wnm=yes
transition-threshold=-70
transition-threshold-time=10s
transition-request-period=20s
transition-request-count=2
transition-time=30s
multicast-enhance=enabled
local forwarding / traffic processing on CAP
Sanitized MikroTik evidence
RouterOS=7.22.2
controller=hEX S
CAPs=5x hAP ax S
CPU during issue=low, around 3 to 5 percent in captured profile
wireless CPU around 0.5 percent in captured profile
CAP summary:
CAP-1 state=Ok version=7.22.2
CAP-2 state=Ok version=7.22.2
CAP-3 state=Ok version=7.22.2
CAP-4 state=Ok version=7.22.2
CAP-5 state=Ok version=7.22.2
5 GHz AP config summary:
AP-1 if=cap-wifi1 ssid=SSID-5G band=5ghz-ax width=20/40mhz freq=5180,5200 auth=wpa2-psk ft=yes ft-over-ds=yes connect-priority=0/1 multicast-enhance=enabled rrm=yes wnm=yes threshold=-70
AP-2 if=cap-wifi4 ssid=SSID-5G band=5ghz-ax width=20/40mhz freq=5180,5200 auth=wpa2-psk ft=yes ft-over-ds=yes connect-priority=0/1 multicast-enhance=enabled rrm=yes wnm=yes threshold=-70
AP-3 if=cap-wifi6 ssid=SSID-5G band=5ghz-ax width=20/40mhz freq=5540,5560 auth=wpa2-psk ft=yes ft-over-ds=yes connect-priority=0/1 multicast-enhance=enabled rrm=yes wnm=yes threshold=-70
AP-4 if=cap-wifi8 ssid=SSID-5G band=5ghz-ax width=20/40mhz freq=5500,5520 auth=wpa2-psk ft=yes ft-over-ds=yes connect-priority=0/1 multicast-enhance=enabled rrm=yes wnm=yes threshold=-70
AP-5 if=cap-wifi10 ssid=SSID-5G band=5ghz-ax width=20/40mhz freq=5220,5240 auth=wpa2-psk ft=yes ft-over-ds=yes connect-priority=0/1 multicast-enhance=enabled rrm=yes wnm=yes threshold=-70
Fast client example:
CLIENT-FAST if=cap-wifi1 signal=-65 auth=ft-wpa2-psk band=5ghz-ax tx-rate=309.7Mbps to 413.0Mbps rx-rate=390.0Mbps to 413.0Mbps
Slow client example:
CLIENT-SLOW if=cap-wifi1 signal=-58 to -64 auth=ft-wpa2-psk band=5ghz-ax tx-rate=54.0Mbps rx-rate=325.0Mbps to 458.8Mbps
Other observed slow-style row:
CLIENT-OTHER if=cap-wifi6 signal=-49 auth=ft-wpa2-psk band=5ghz-ac tx-rate=54.0Mbps rx-rate=400.0Mbps
Interpretation:
Same AP, same SSID, same channel, similar signal.
One station is fast.
Another station is stuck at CAP-to-client tx-rate=54Mbps.
Question
Which MikroTik WiFi/CAPsMAN setting or known RouterOS WiFi behavior can cause a per-station CAP-to-client TX rate to stick at 54 Mbps, while another client on the same AP/channel is fast?
