Troubleshooting random wireless disconnections from AP

[fizikz]

modem --> router/wifi1 --> powerline --> AP/wifi2

router = Engenius ESR9850
powerline = TP-Link PA511 Kit
AP = TP-Link WR841N

wifi1 and wifi2 use same SSID

I have my home network setup as above. Most devices connect to the wireless AP on wifi2. But sometimes internet connectivity drops for the AP's wireless clients. They still seem to remain "connected" to the AP, but nothing is reachable, including the AP's own web interface.

If I connect to the router/wifi1 during disconnection events, everything works fine, i.e. internet, and even the ability to reach the AP's web interface. If I connect back to wifi2, which succeeds, the internet and AP web interface may still be unreachable.

The disconnections persist for a few minutes then get resolved on their own. Rebooting the AP seems to fix it too. I'm not certain, but I think wired clients of the AP do not experience issues.

I've upgraded to the latest TP-Link firmware, but I might try ddwrt if that could help. Recommended right now?

What could be the problem? I ruled out the powerline since I can reach the AP through router during disconnections. The AP's wireless doesn't seem to drop the clients. So maybe an IP issue? DHCP? (some clients use dynamic IPs, others use static, all wireless clients of the AP seem affected) Would the AP or the router be at fault? What could I do to test?

 

[degrub]

Are the APs running different radio channels ? Sounds like rf interference.
What is the signal strength of each wireless radio at the client device location when the loss of internet occurs ?
You could assign different ssids to help find the issue.
If you have an IOS device you can get the Apple Airport utility from the store and check the signal strength via wifi scan and check for other radio interference from your neighbors at the same time.

Do plug in a device to the APs other lan ports (if exist) and directly to the powerline modem to verify you don't have a powerline or AP issue.

 

[fizikz]

Thanks for the reply and suggestions, degrub.

The radios are on different channels, 6 and 11. I doubt it's a signal strength issue since all devices connected to the wireless AP lose connectivity (but don't seem to get dropped as clients), including devices directly on top of and in the same room as the wireless AP. Those devices report 4 or 5 "bars" even during these issues.

I doubt rf interference as my area isn't very congested. Using LinSSID (similar to inSSIDer) I currently detect six radios, two of which are my own.

The SSIDs are the same for both wifi1 and wifi2, but on my linux device, I can choose to connect to a specific AP by MAC address or BSSID, which is how I verified that the router and even the AP's web interface are reachable during disconnections.

To be clear, I don't have a powerline modem or router. A powerline adapter kit is used as the link between the router and AP.

There is a computer and printer plugged into the AP's other LAN ports. Unfortunately the computer isn't always powered on or in use when the random internet drops happen. However, so far it would seem LAN devices are not affects. I'll try accessing the printer's web interface next time the issue occurs.

 

[fizikz]

I don't know if this is helpful, but I'll mention it just in case: the AP's log shows the following chunk of entries roughly every 74 minutes. Note that DHCP is disabled on the AP. Also, they are INFO level log entries, so I assume they don't imply any error.

Index; Time; Type; Level; Log Content
168; 4th day 22:03:24; DHCP; INFO; DHCPC DHCP Service unavailable, recv no OFFER
167; 4th day 22:03:22; DHCP; INFO; DHCPC Send DISCOVER with request ip 0 and unicast flag 1
166; 4th day 22:03:20; DHCP; INFO; DHCPC Send DISCOVER with request ip 0 and unicast flag 1
165; 4th day 22:03:16; DHCP; INFO; DHCPC Send DISCOVER with request ip 0 and unicast flag 0
164; 4th day 22:03:14; DHCP; INFO; DHCPC Send DISCOVER with request ip 0 and unicast flag 0
163; 4th day 22:03:12; DHCP; INFO; DHCPC Send DISCOVER with request ip 0 and unicast flag 0

 

[fizikz]

This morning, the wireless AP's (wifi2) is down. It's unusual in that it hasn't returned in a few minutes as most times. This gave me a chance to verify that the printer connected by LAN to the wireless AP's switch is reachable. However the wireless AP's IP is not. I cannot connect to wifi2 (wireless AP). And when connected to wifi1 (router), I cannot access the wireless AP's web admin page, and pings to it's IP say "destination host unreachable." What could be the problem?

EDIT: I checked with LinSSID that both radios are active (and strong signal from wireless AP: ~ -37dB). I also tried connecting to the wireless AP from another device to make sure the connection issue wasn't a problem with my laptop.

EDIT2: Confirmed network/internet access for the computer with wired LAN connection to the wireless AP. That computer is also unable to connect to the wireless AP's IP.

 

[sfx2000]

powerline = TP-Link PA511 Kit

That's the problem in a nutshell - the random dropout is a "known" issue with the TP-Link PLC's....

 

[fizikz]

Wow, I had no idea there were so many reports of dropout issues with TP-Links powerline units. But in this case, if the powerline is the problem, how would the AP's wired clients not also experience the disconnections? Maybe the wired recovers faster and is less perceptible?

Right now I've flashed the wireless AP to dd-wrt. I'll see if that makes any difference, and maybe look into replacement powerline units... Is there a way to diagnose powerline or at least see status/settings without connecting to them physically?

 

[fizikz]

I've been running different versions of dd-wrt on the AP (TP-Link WR841Nv8) for several months (currently on build r31899) and have not noticed any more of the "connected but nothing reachable over wifi" drops.

 

[sfx2000]

Wow, I had no idea there were so many reports of dropout issues with TP-Links powerline units.

Search the google - there's a patch that disables power-saving for some of the TP-Link PLC's, and that helps much - doesn't completely solve the issue, but it does help.

The reality however - with a TP-Link AV1200 kit, on a cross circuit run over 35 feet - the effective rate was around 350Mbps, and the real-world thru-put across that pair, in my case, was 100Mbps (source to sink) over iPerf3 from client to self-hosted server...

Good enough for lightweight work, and cheaper than running a cable - I picked up this kit as I was doing some remodeling in the home, so we had to move the TV/AV complex to another room that did not have an existing ethernet drop..

 

[sfx2000]

powerline = TP-Link PA511 Kit

And FWIW - TP-Link did a campaign to recall/refund these adapters some time back due to performance issues that could not be resolved - that has since expired...

Impacted PLC kits/adapters...

• TL-PA511
• TL-PA511KIT
• TL-PA4010
• TL-PA4010KIT
• TL-WPA4220
• TL-WPA4220KIT

Could always reach out nicely to TP-Link Tech Support and ask for a goodwill swap out.

 

[fizikz]

And FWIW - TP-Link did a campaign to recall/refund these adapters some time back due to performance issues that could not be resolved - that has since expired...

Impacted PLC kits/adapters...

• TL-PA511
• TL-PA511KIT
• TL-PA4010
• TL-PA4010KIT
• TL-WPA4220
• TL-WPA4220KIT

Could always reach out nicely to TP-Link Tech Support and ask for a goodwill swap out.

Wow, it must be serious if they had a recall. I contacted Tech Support, but they mentioned it's both expired and was not offered in Canada. They told me I could email the sales department, in case they might accommodate me somehow. It's been a week and they haven't responded.