3702i slow download speeds

[CourtneyKPrin]

WLC 5508 environment with many 3702i and 3802i APs. There is one 3702i that slows a client's download speeds and the upload speeds appear normal. With one to two devices connected to the AP, the iperf download speeds are around 20 Mb/s (using -R). The iperf upload speeds are around 125 Mb/s. I replaced the problem AP with a spare 3702i and the client's download speeds are around 100 Mb/s (using -R). With the problem AP on the bench, I have done the format flash and recovery image process with no difference (~20 Mb/s using iperf -R). The clients are connecting with 5Ghz channels. Any thoughts on what would cause this? Would the AP complain if an internal antenna was malfunctioning?

[Scott Fella]

The ap wouldn’t know if the antenna is failing only if the radio was faulty. Factory reset the ap and join it back, if the issue persists using the same channel width and channel as another ap in a different area or just with rrm, then I would say the ap is faulty. We have had a few 3702’s go bad and has them replaced. They are pretty old.

[Leo Laohoo]

What firmware is the WLC running on?

Check the AP GigabitEthernet interface for any line errors.

[CourtneyKPrin]

There are no errors on the switchport interface the AP is connected to and the AP is connected at 1000Mb/s full duplex. Is there a command to check this on the AP cli? Before I did the format flash I did a factory reset through the WLC with no difference.

[Scott Fella]

If your factory reset, go ahead and flash it. I don’t think that is going to do anything. You already swapped the ap and changed the switch port and patch cable, so just go ahead and flash it. If you did see errors, then you would suspect a bad port, which is not because you have another ap in place, a bad cable rumor patc, which again it’s not because of the previous statement, and or a bad Ethernet port on the ap, which means it’s broken.

[Leo Laohoo]

Remote or console into the AP and post the complete output to the command "dir".

[CourtneyKPrin]

WLC is running 8.5.171

Directory of flash:/

2 -rwx 274 Jan 1 1970 00:23:26 +00:00 info
3 -rwx 368 Oct 18 2021 10:15:51 +00:00 capwap-saved-config-bak
4 drwx 576 Jan 1 1970 00:26:29 +00:00 ap3g2-rcvk9w8-mx
14 drwx 2368 Oct 15 2021 20:12:43 +00:00 ap3g2-k9w8-mx.153-3.JF14
15 -rwx 0 Mar 1 1993 00:00:35 +00:00 config.txt
16 -rwx 74738 Oct 15 2021 20:16:47 +00:00 event.log
17 drwx 0 Mar 1 1993 00:01:03 +00:00 configs
82 -rwx 368 Oct 15 2021 22:01:04 +00:00 capwap-saved-config
83 -rwx 314 Oct 18 2021 13:23:26 +00:00 env_vars
84 -rwx 64 Oct 15 2021 20:16:44 +00:00 sensord_CSPRNG0
85 -rwx 12312 Oct 18 2021 10:16:27 +00:00 private-multiple-fs
86 -rwx 64 Oct 15 2021 20:16:44 +00:00 sensord_CSPRNG1

40900608 bytes total (19680256 bytes free)

To summerize, I have taken the following steps but still have slow download speeds on one 3702i:

Reset AP via WLC

Format flash AP via cli

Moved to known good cabling and switch

[Scott Fella]

I really think that you did enough to isolate the issue to a bad ap.  If you really want to keep going, test on 2.4ghz and 5ghz separately and see if maybe the issue is with one radio or not.  You can also play around with that ap and configure it for autonomous and do the same test.  If the slowness is still there, I don't think that is something that is fixable, but that is me from my experiences with ap's going bad.

[Leo Laohoo]

No signs of bad radio.  
I do not see any radio core files. 

The event logs matches the same stamps when the new IOS got downloaded. 

The sensor logs matches the same stamps with the new IOS.  

[CourtneyKPrin]

I investigated two other 3702i APs today that had reports from users of bad wifi and found the same symptoms, slow iperf download speeds. I swapped out the two APs with spare 3702i APs and the download speeds appear to be normal now. I did not factory reset the problem APs, but the replacements were factory reset before I installed them. I'll take the problem APs back to my desk and verify I can recreate the problem and try a factory reset. I'll also try one in autonomous mode and see what happens. I really want to know how many other 3702i's are having the same symptoms, but I'd rather not do an iperf test on each one.

[Leo Laohoo]

What firmware is the WLC running on? 

Has anyone rebooted the AP when the complaints happen (before replacing the AP)?

[CourtneyKPrin]

The WLC is running 8.5.171

I restarted the first AP I was troubleshooting right before I replaced it last week. The two problem APs I worked on today hadn't been restarted in 68 days.

[Leo Laohoo]

So does the reboot of the AP alleviate the problem?

[Scott Fella]

The one ap he swapped out and booted up by his desk still has issues. That’s why I think the device is just going bad. 

[Leo Laohoo]

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@Scott Fella wrote:

The one ap he swapped out and booted up by his desk still has issues. 

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Gotcha, @Scott Fella.

In that case, I agree and the AP could be failing.