Strange WiFi failure and admin sluggishness

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Strange WiFi failure and admin sluggishness

Saturday afternoon, my Airport Time Capsule (the 802.11ac model) had its WiFi network suddenly stop working for all devices in our household. My initial thought was interference, but I used the Mac app WiFi explorer, and the signal level was high, and the noise level was very low for all four networks from the TC (2.4GHz/5GHz, regular/guest). I could also see all the usual neighbor networks (all at low signal levels). The 2.4 GHz band was crowded with a half dozen neighbors showing up at low signal levels. The 5GHz band had only two other households showing, however, they were using different channels(chan 56,-1 for one, 157 for the other, the TC was on 132). The TC networks would drop out periodically on the signal tracker, then reappear. Wired internet connections though the TC were working perfectly fine, however, so it wasn't a problem with the ISP.

To try to diagnose the problem, I fired up Airport Utility. It couldn't reach the TC at all over wireless, but it could see it on the wired LAN. However, the TC was responding very sluggishly, asking repeatedly for the admin password (which is in my keychain) before it finally allowed access. I tried various channel values for both the 2.4 and 5 GHz bands, without any useful effect. Every time the TC was reconfigured, it never reconnected with Airport Utility, and I had to prod it several times and give the password again before it finally allowed access. (The details popover generally took over a minute to appear after giving the password.) I also tried resetting the TC to factory settings (not the full reset button method, but using the Airport Utility menu item. No help from that.

I finally called Apple Support, and after some discussion of what I'd tried and seen using WiFi Explorer, we concluded there was probably a hardware problem, and I'd have to take the thing in for service. Then today, everything suddenly started working normally again. The TC is responding quickly to Airport Utility, and not asking for the password repeatedly any more (seems to be getting it from keychain, as it should).

I'm not sure what the problem was, but thought I'd post this here in case anyone else sees similar problems. My best guess now is that there was some kind of attack going on against the TC from the WAN side, causing the TC"s control processor to get bogged down and fail to processing various housekeeping parts of the protocols, or dropping packets headed for the control processor. The fact that it suddenly recovered certainly suggests the problem was environmental in some way, not a hardware, software, or configuration problem.

If anyone else sees something like this, it may be worth trying to get a packet sniffer on the WAN port and see if there's a lot of junk destined to control ports on the Time Capsule.

Time Capsule 802.11ac-OTHER

Posted on Oct 12, 2015 12:30 PM

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Answer 1

Oct 12, 2015 12:57 PM in response to WalterNH

I doubt it is as complicated as that.. drop out of wireless on the AC model AE and TC is regularly reported.

Here is a 7 page thread from the AE Gen6 so same as the TC gen5.

New Airport Extreme (6th Gen) Dropping Connection from Time to Time.

What is the setup.. what modem, make and model please??

Is the TC working as router or bridge?

Unfortunately AC airports are simply not very reliable.

High demand on the WAN side really should not affect LAN.. unless you are on gigabit fibre the pipe to your router is simply too small and apple do not worry about firewall or QoS etc at the router level.

How old is the TC? Do you still have some warranty/applecare on it? If it is less than 2years old even if it is out of warranty you can still buy applecare on a computer or appletv (purchase a new appletv if you need to).. and get it replaced.

The setup matters however..

Particularly with Yosemite we have seen major issues with the airports due to poor network ability of the OS>

I would do the follow at least.

Start from a factory reset. No files are lost on the hard disk doing this.

Factory reset universal

Power off the TC.. ie pull the power cord or power off at the wall.. wait 10sec.. hold in the reset button.. be gentle.. power on again still holding in reset.. and keep holding it in for another 10sec. You may need some help as it is hard to both hold in reset and apply power. It will show success by rapidly blinking the front led. Release the reset.. and wait a couple of min for the TC to reset and come back with factory settings. If the front LED doesn’t blink rapidly you missed it and simply try again. The reset is fairly fragile in these.. press it so you feel it just click and no more.. I have seen people bend the lever or even break it. I use a toothpick as tool.

N.B. None of your files on the hard disk of the TC are deleted.. this simply clears out the router settings of the TC.

Setup the TC again.

Then redo the setup from the computer with Mavericks--Yosemite--ElCapo. (MYELCAP)

1. Use very short names.. NOT APPLE RECOMMENDED names. No spaces and pure alphanumerics.

eg TCgen5 for basestation and TCwifi wireless name.

If the issue is wireless use TC24ghz and TC5ghz with fixed channels as this also seems to help stop the nonsense. But this can be tried in the second round. ie plan on a first and second round of changes to fix this.. hopefully.. I will point out other steps that can be round2.

2. Use all passwords that also comply with 1. but can be a bit longer. ie 8-20 characters mixed case and numbers.. no non-alphanumerics.

3. If the TC is main router you can skip this point. This is only an issue when the TC is bridged.

Ensure the TC always takes the same IP address.. you will need to do this on the main router using dhcp reservation.. or a bit more complex setup using static IP in the TC. But this is important.. having IP drift all over the place when MYELCAP cannot remember its own name for 5 min after a reboot makes for poor networking.

4. Check your share name on the computer is not changing.. make sure it also complies with the above.. short no spaces and pure alphanumeric.. but this change will mess up your TM backup.. so be prepared to do a new full backup. Sorry.. keep this one for second round if you want to avoid a new backup.

5. Mount the TC disk in the computer manually.

In Finder, Go, Connect to server from the top menu,

Type in SMB://192.168.0.254 (or whatever the TC ip is which you have now made static. As a router by default it is 10.0.1.1 and I encourage people to stick with that unless you know what you are doing).

You can use name.. SMB://TCgen5.local where you replace TCgen5 with your TC name.. local is the default domain of the TC and doesn't change.

However names are not so easy as IP address.. nor as reliable. At least not in Yosemite they aren't. The domain can also be an issue if you are not plugged or wireless directly to the TC.

6. Make sure IPv6 is set to link-local only in the computer. For example wireless open the network preferences, wireless and advanced / TCP/IP.. and fix the IPv6. to link-local only. Do the same for ethernet if you use it.

There is a lot more jiggery pokery you can try but the above is a good start.. if you find it still unreliable.. don't be surprised.

You might need to do some more work on the computer itself. eg Reset the NVRAM/PRAM/SMC.. has helped some people. Clean install of the OS is also helpful if you upgrade installed.

Tell us how you go.

If the issue happens again as I suspect it will .. take the TC to apple for replacement.

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Answer 2

WalterNH Author

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Oct 12, 2015 6:47 PM in response to LaPastenague

LaPastenague wrote:

I doubt it is as complicated as that.. drop out of wireless on the AC model AE and TC is regularly reported.

Here is a 7 page thread from the AE Gen6 so same as the TC gen5.

New Airport Extreme (6th Gen) Dropping Connection from Time to Time.

What is the setup.. what modem, make and model please??

Is the TC working as router or bridge?

Unfortunately AC airports are simply not very reliable.

High demand on the WAN side really should not affect LAN.. unless you are on gigabit fibre the pipe to your router is simply too small and apple do not worry about firewall or QoS etc at the router level.

How old is the TC? Do you still have some warranty/applecare on it? If it is less than 2years old even if it is out of warranty you can still buy applecare on a computer or appletv (purchase a new appletv if you need to).. and get it replaced.

The setup matters however..

Particularly with Yosemite we have seen major issues with the airports due to poor network ability of the OS>

TC model: Airport Time Capsule 802.11ac 3TB-USA ME182LL/A

Cable modem: Motorola Surfboard SB6141 DOCSIS 3.0, ISP is Comcast.

Running in router mode (DHCP/NAT), WAN admin is turned off, config is basically default except for network name and passwords.

No additional wireless nodes, there's a wired network with a couple Netgear 100Mb switches hanging off one LAN port, and a Philips Hue hub off another, the third LAN port is unused.

There are three iPhones (two 4s and one 6), three iPads (two Airs and one Air 2), and four or five Macs using the wireless network, plus a gen2 Apple TV. The iOS devices are all on 8.4 I think, except one 4s is still running iOS 6. The Macs are mostly on 10.10, though I think one is still on Mountain Lion.

The TC is a few weeks out of warranty, but there's AppleCare+ on my daughter's iPad, and the Apple tech I talked to said that should cover any issues with the TC.

The symptoms don't seem similar to the problems in the thread you quoted. The TC has been running just fine for a bit over a year, with only one minor problem with my Macbook Pro (5GHz WiFi dropped out when the machine was running 3D games and got hot, 2.4G still worked fine). Then suddenly, no WiFi device in the house was working for most of two days, and just as suddenly, everything was fine again. WiFi Explorer showed the signal strength as excellent during the outage, with S/N ratio around 55dB and very low noise (neighboring houses showed poor signals with S/N around 0dB or less, and high noise). So the obvious answer, interference, seemed to be ruled out. There was very minimal wireless connectivity -- occasionally a notification would get through to an iPhone, and I could do trace routes from my Macbook, but the first hop latencies (i.e. to the TC itself) were 100-500 ms, and packet loss rates seemed to be 50+%.

The wired LAN side of the TC continued to work flawlessly through the whole outage, with no signs of dropped packets or unusual latencies (we were playing MMORPGs through this without issues). However, connections over the LAN to the TC using Airport Utility were very flakey, with long latencies, frequent re-requests for the password, and general non-responsiveness. This all disappeared when everything started working again, and the TC is alms instantly responsive to Airport Utility again.

After dismissing interference as a likely problem (that shouldn't have affected the LAN admin sessions, for one thing), my next hypothesis was that some kind of hardware issue (e.g. continuous interrupts) was bogging down the TC's CPU. But the device recovered on its own, and not when anything was being done with it physically. That's not the usual pattern I've seen with hardware failures. Usually they're either permanent or intermittent with physical access or thermal changes. None of that was happening here.

That leaves me with the "WAN traffic overloading the CPU" hypothesis. It's actually not hard to overload a router's control plane, especially in a device with a lower end CPU like home routers have. While the incoming link couldn't saturate the fast path in the TC's switch, and unroutable packets being dropped should also be handled in the fast path hardware, traffic on the slow path, up through the TC's CPU, is a different matter. It also depends on what the control traffic is doing -- if it needs crypto operations, like password checking or HTTPS setup, that can easily tax a low-end processor. A flurry of too-large packets needing fragmentation could also be a problem. Given that attacks on home routers are becoming popular now, I am wondering if something was trying to brute-force access to the TC's admin software. With the WAN admin shut off, though, I wouldn't expect that traffic to be routed to the CPU at all, just dropped. I wish I'd had a sniffer on the WAN link at the time, but I don't have one handy.

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Answer 3

Oct 12, 2015 7:57 PM in response to WalterNH

Cable modem: Motorola Surfboard SB6141 DOCSIS 3.0, ISP is Comcast.

This is known problem.. with both AE and TC .. not much on earlier models but the AC has lots of issues.. and it can very strangely start after it has worked fine for 12months.

But that would tend to have issues on both ethernet and wireless connections.. so I am not sure.

I would test with a cheap router in place of the TC.. and bridge the TC and use it just for wireless and TM backups.. see how it goes..

You don't need to spend a lot because you want routing not wireless.. eg TP-Link bottom gigabit model, WR1043NDv2 is around $50 in the US I should think.. and it is quite powerful and reliable.. well worth it for a test.

It will prove the issue and provide an alternative to your WAN sniffer.

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