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Simple sounding question. When the wifi is turned on, our small office DSL speeds drop to 0.3 Mbps, with ping up around 1.4 seconds, for both wired and wireless clients. Turning the wifi off instantly picks the speed back up to decent DSL sync rates.

I've tried the changing wifi password to check for leechers. Didn't make a difference. The router doesn't show any unknown devices.

The problem started the day after we picked up a new ADSL modem. But on the same day 20 people moved into the office below us, so it's hard to pinpoint the issue.

I'm seriously stumped.

Our network:

Internet - Linksys X3000 DSL modem [wifi always off] - Netgear JGS516 Gigabit switch - Apple Airport Extreme Base Station

There are 3 Macs and a printer plugged into the switch (via a patch panel). On the Airport Extreme's wifi there are 2 PCs and 2 Macs, plus a handful of iOS devices, but it doesn't matter, because even if the wifi devices are off, the speed is still slow.

The problem continues if I plug the Airport directly into the modem.

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4 Answers

up vote 1 down vote accepted

One of the guys on the network was running Backblaze to do continuous cloud backups. Seems it was overwhelming the Linksys X3000 router.

Speeds were fine when I swapped out the router, and then after we discovered that Backblaze being turned on correlated perfectly with the network going slowly, we turned it off, and the speed picked up again.

It was hard to pin down because the backups weren't running continuously.

Only weird thing is that the speed didn't always pick back up when the problem client disconnected from the network. I wonder if that's a symptom of whatever caused the Linksys to dislike Backblaze?

Other weird thing: Dropbox syncing continuously from 4 separate machines (with no rate limit) doesn't cause any issues.

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(I would have posted a comment but can't do it yet so I'll try to formulate this as a decent answer....)

There might be some kind of a packet storm hogging the LAN bandwidth (thus also making internet connection appear to be slow) - have you checked if your LAN contains any weird traffic during the time the network is slow? Such a condition might even be visible observing the activity LEDs in the switch when the wifi is swithed on/off when the LAN should otherwise be mostly idle. This would probably need to be related to some conflict with your wifi and e.g. the wifi in the office downstairs from you. Maybe you could try selecting different frequencies/channels for your wifi to rule this one out.

You also mention setting up a new DSL box, so there could also be some routing issue, but did the issue start immediately after setting the new DSL box or only the next day?

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If this is happening for both wired and wireless users then its probably not wireless interference as this would only affect wireless users. Are you saying this happens when the wireless settings are simply enabled on the airport and no clients are connected at all?

Right now I'd say that the airport was flat-out faulty, if it wasn't for it presumably working before you replaced the ADSL modem. Try running wireshark against it to see what sort of traffic it puts onto the LAN when the wireless is enabled.

Lastly how are you connecting it? You're not using the WAN port on it to connect it to the rest of your LAN are you?

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I'll fire up wireshark and see what I find. Connecting via the WAN port vs. standard ports makes no difference to the problem :-( –  christianlinnell Aug 18 '13 at 22:13
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I would set the Linksys X3000 to bridged mode only and configure the Apple Airport Extreme Base Station to do the PPOE that is necessary for your DSL. Your network would look like the layout below.

Internet -> Linksys X3000 Bridged -> Apple Airport Extreme Base Station PPOE -> Netgear switch -> devices

There's no reason to be running two full routers in this scenario.

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The Airport won't do PPPoA unfortunately, and our provider seems to require it. It's just running in bridge mode right now so it should be running as a dumb AP anyway, right? The easiest thing would be to try replacing the Airport with a different kind of AP, but frankly, I'd prefer to fix the problem. We can't just turn on the wifi on the router as it's in a signal dead zone (fantastic architecture). –  christianlinnell Aug 16 '13 at 4:35
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