Wifi Problem I can't solve.

jef

USG Flex 700 as the wifi controller. WAX630S as the AP. Both on the latest firmware.

The problem: The wifi bandwidth drops to zero, or starts about 400Mpbs then stalls until it hits zero and the test will timeout or stumbles down to 5 or 6 mpbs until the test is over. If you are in a shh shell over wifi the bash will hang, then if you are lucky is will resume. If you are on the web, it will time out.

The connected device can be a phone, laptop or computer, etc. Wifi connects fine, speed tests are great 600 (when it is working) both up and down, speeds are what to be expected. The wifi world is a happy place. Then it is not.

There aren't any "Security Services" licensed. So, the IPD and other things that slow everything down should not be a factor. The dash doesn't show the CPU or ram or network loaded, if fact almost nothing is running through this device, I moved it to bench because I can't let others on it until it works.

I moved the USG and the AP to a bench, to eliminate the possibility of bad wires and traffic. The USG Wired works great, the VPN tunnels stay up.
Wired clients (which are servers I wired in to test) are rock solid with full 1G wired bandwidth.

I simply can't figure out why WIFI clients work perfect then stall to a zero.
Doesn't matter if I reboot anything, or reconnect them to the SSID.
I do have 1 SSID doing 5g and 2.4g. It seems to work, the "Session" info shows the clients connection at 5 and the old cameras connecting at 2.4.
The 2.4 seems good. I can (while testing) stream a security camera to a laptop (5gh band) both devices on the Wifi and the video doesn't drop and the camera is 2.4 wifi.

But on another device, you can start browsing the web, and it might work fine for a hours, but at some point it will stop working properly with the loss of bandwidth.

Another example.. Cellphone on WIFI.. Calls over wifi.. yes yes yes yes.. No.
Meaning, you can connect to wifi, make a call over wifi and it works perfect, over and over.. Then for an unknown reason, the same phone in the same spot without any changes, the WIFI call doesn't work. Wont even begin to connect.

I have messed with all the settings nothing changes.
I have changed DNS doesn't make a difference.
I have disable the non licesnsed and should be disabled "Security Stuff" no change.
I even changed out the AP for one from another building and a different AP made no change the problem. I changed the power settings on the AP, I added a 2nd AP, nothing changed the issue where at some point wifi clients get 0 bandwidth randomly.

At one point I thought that lan traffic over wifi was good, while the internet traffic was the problem. But that idea eventually faded, when being connect lan to lan over wifi would lock up. The inconsistency of the problem makes it hard.

I do not have any more ideas, or know where to look for clues to debug Zyxel Wifi.

These devices are in a semi remote location, there isn't any other wifi interferece.
The Unifi wifi setup prior to this did not have any issues.

Sorry this write up is so long. I have been messing with it for 2 weeks, trying everything I could think of, I don't know where to turn. Help would be great, a fresh idea of what might cause the wifi to be connected, but not have through put. It doesn't appear to be a dns lookup issue.

Zyxel_Melen

Hi @jef

Since you've already done some cross-checking, could you please create a new SSID that uses only the 5GHz band and has the same radio and SSID settings as your current SSID, and then immediately perform DCS on this new SSID to find a suitable channel? This would help reduce variables and make it easier for us to investigate the problem. Please also collect the diagnostic file once the issue happens again.

Here is the guide FAQ for you to reference:

https://community.zyxel.com/en/discussion/18869/how-to-collect-the-standalone-ap-diagnostic-info-by-gui

jef

Will do. I wont have time today, but now I have a new direction I'm on it. Thank you.

Zyxel_Melen

Hi @jef

Great. Please feel free to update here in anytime or send me a message.

jef

I collected diag data when the problem was happening before making a 5Ghz only SSID.
Then I created a different SSID 5Ghz only.
Everything seemed fine for a while, then I noticed the device I was on (connected to the 5G only ssid) would hang waiting for network data. The web tool "Slack" would hanging "waiting for connection".
I collected another diag, this when there were 2 SSIDs and while exhibiting the poor wifi condition.
I also collected AP diag data,

A speed test using "Fast.com" results are 17Mbps when the problem is manifesting, the normal is anywhere from 600-800Mpbs on the same device when wifi is working well.

I really hope this is something stupid I have done wrong. I will gladly shoulder the embarrassment for a solution.

What should I do with the diag files:
diaginfo-2026-07-01_19-13-28.tar.bz2
diaginfo-2026-07-02_16-31-01.tar.bz2
apdiaginfo-FC22F4D7E287-2026-07-02_16-50-28.tar.bz2
apdiaginfo-D8ECE5B712F6-2026-07-02_16-48-31.tar.bz2

Zyxel_Melen

Hi @jef

I will send you a message to get these files. Please share them in the message. Thanks!

jef

I have notice a few other oddities. Maybe they will help.
I put a wifi phone on static ip address, I noticed in dhcp table it was stacking up alot of borrowed DHCP addresses, seems samsung uses virtual mac addresses, so phones like these can not be dhcp mapped.

With the static IP, the ping was mostly hit and miss.
Yet a laptop connected to the same AP, the ping is solid.

When I try and trace route the static ip.. 83.6% loss. 192.168.25.7 to 192.168.25.149 same lan.

The wifi strenght is in the great.

So.. wifi clients that have the problem the packets are going?
….
64 bytes from 192.168.25.149: icmp_seq=56 ttl=64 time=16.6 ms
64 bytes from 192.168.25.149: icmp_seq=57 ttl=64 time=3.69 ms
no answer yet for icmp_seq=58
64 bytes from 192.168.25.149: icmp_seq=59 ttl=64 time=4.54 ms
no answer yet for icmp_seq=60
no answer yet for icmp_seq=61
no answer yet for icmp_seq=62
64 bytes from 192.168.25.149: icmp_seq=63 ttl=64 time=4.37 ms
no answer yet for icmp_seq=64
no answer yet for icmp_seq=65
no answer yet for icmp_seq=66
no answer yet for icmp_seq=67
no answer yet for icmp_seq=68
no answer yet for icmp_seq=69
no answer yet for icmp_seq=70
64 bytes from 192.168.25.149: icmp_seq=71 ttl=64 time=9.28 ms
64 bytes from 192.168.25.149: icmp_seq=72 ttl=64 time=28.9 ms
no answer yet for icmp_seq=73
no answer yet for icmp_seq=74
64 bytes from 192.168.25.149: icmp_seq=75 ttl=64 time=7.86 ms
no answer yet for icmp_seq=76
no answer yet for icmp_seq=77
no answer yet for icmp_seq=78
no answer yet for icmp_seq=79
64 bytes from 192.168.25.149: icmp_seq=80 ttl=64 time=53.1 ms
no answer yet for icmp_seq=81
64 bytes from 192.168.25.149: icmp_seq=82 ttl=64 time=5.78 ms
64 bytes from 192.168.25.149: icmp_seq=83 ttl=64 time=5.24 ms
64 bytes from 192.168.25.149: icmp_seq=84 ttl=64 time=3.54 ms
no answer yet for icmp_seq=85
no answer yet for icmp_seq=86
no answer yet for icmp_seq=87
no answer yet for icmp_seq=88
64 bytes from 192.168.25.149: icmp_seq=89 ttl=64 time=39.1 ms
no answer yet for icmp_seq=90
no answer yet for icmp_seq=91
no answer yet for icmp_seq=92
no answer yet for icmp_seq=93

jef

When WIFI is working correctly..
If I ping from the Phone to the computer the ping is solid.
If I ping from the computer to the Phone the ping is solid.
When I do a network bandwidth test on the phone, perfect 700Mbps of a possible 1G.

Nothing has changed except time from a horrible ping and huge packet loss to perfect.
That rules out hardware, I think.

Now..
If I turn wifi on the phone off.. Then turn wifi back ON on the phone, it will attach to the same SSID.
But the connection is horrible again.

64 bytes from 192.168.25.149: icmp_seq=3 ttl=64 time=278 ms
64 bytes from 192.168.25.149: icmp_seq=4 ttl=64 time=300 ms
64 bytes from 192.168.25.149: icmp_seq=5 ttl=64 time=323 ms
64 bytes from 192.168.25.149: icmp_seq=6 ttl=64 time=346 ms
64 bytes from 192.168.25.149: icmp_seq=7 ttl=64 time=882 ms
64 bytes from 192.168.25.149: icmp_seq=8 ttl=64 time=95.6 ms
64 bytes from 192.168.25.149: icmp_seq=9 ttl=64 time=68.2 ms
64 bytes from 192.168.25.149: icmp_seq=10 ttl=64 time=46.7 ms
64 bytes from 192.168.25.149: icmp_seq=11 ttl=64 time=65.9 ms

Turn WIFI off on the phone.
no answer yet for icmp_seq=12
no answer yet for icmp_seq=13
no answer yet for icmp_seq=14
no answer yet for icmp_seq=15
no answer yet for icmp_seq=16
no answer yet for icmp_seq=17
no answer yet for icmp_seq=18

Turn WIFI back ON on the phone.
64 bytes from 192.168.25.149: icmp_seq=19 ttl=64 time=72.3 ms
64 bytes from 192.168.25.149: icmp_seq=20 ttl=64 time=4.59 ms
64 bytes from 192.168.25.149: icmp_seq=21 ttl=64 time=31.7 ms
64 bytes from 192.168.25.149: icmp_seq=22 ttl=64 time=159 ms
no answer yet for icmp_seq=23
no answer yet for icmp_seq=24
no answer yet for icmp_seq=25
no answer yet for icmp_seq=26
no answer yet for icmp_seq=27
no answer yet for icmp_seq=28
no answer yet for icmp_seq=29
no answer yet for icmp_seq=30
no answer yet for icmp_seq=31
no answer yet for icmp_seq=32
no answer yet for icmp_seq=33
no answer yet for icmp_seq=34
no answer yet for icmp_seq=35
64 bytes from 192.168.25.149: icmp_seq=36 ttl=64 time=68.6 ms
no answer yet for icmp_seq=37
no answer yet for icmp_seq=38
no answer yet for icmp_seq=39

Now when I ping from the Phone to the computer it is still 100% perfect ping.

But at the same time the computer can NOT ping the phone.. "No Answer from ICMP".

no answer yet for icmp_seq=34
no answer yet for icmp_seq=35
64 bytes from 192.168.25.149: icmp_seq=36 ttl=64 time=68.6 ms
no answer yet for icmp_seq=37
no answer yet for icmp_seq=38
no answer yet for icmp_seq=39

So… that tells me what?

WIFI sees LAN .. LAN does not always see WIFI.

So. when WIFI is acting bad, it is because traffic isn't getting back from the WAN / LAN to the wifi?

jef

I have a Lan to Wan policy.. any to any.
But WIFI is on the same "Lan" (dhcp leg of the network) so there is no rule for AP to Lan or WIFI to lan. Should not be a need.

And why would it work sometimes but not always if I was missing a route. And you don't really have to "route" on the same broadcast mask. WIFI and LAN are the same subnet. So…. Do APs have to route back to that LAN? And does that mean the wired LAN has to route to APs even on the same subnet?

It should just work right..

jef

I do not have "layer-2 isolation" on, if I did wifi to lan should never work, not be sporadic.

Vlan settings are not overwritten on the AP (aps, I added a 2nd when messing with stuff). They both should be the default vlan id: 1 .. Since clients get a correct dhcp I assume this is fine.

I do have IPSEC tunnels, but the remote subnets are different from the local LAN subnet.

WiFi subnet zone to the LAN/Destination subnet zone. Are the same DHCP zone, or is that a problem?
Am I required to have the WIFI clients on a seperate subnet and route them to the LAN?

PeterUK

change the Wifi LAN IP/subnet on Flex 700 to 10.255.0.1/24 and test