Time Capsule / Airport Extreme - extremely poor NAT performance

[ryanobjc]

Hi folks,

A few months ago I got the new time capsule (-ac edition), and all was well. Then I started having network performance issues. I was unable to download fast, and I did an extended troubleshooting experience with my ISP.

We came to the conclusion that the only piece of networking gear that could be causing performance issues was the Time Capsule. So I ended up getting a retail replacement at the apple store, and all was well.

Until today.

I was seeing extremely poor download performance on download.jetbrains.com - normally I can get a solid 1-3MB/sec out of this. All of a sudden I was getting insanely poor performance. So I grab my trusty speedtest.net and low and behold my 35/2 is now more like 2/0.2.

Now I know what you're going to say - WIRELESS INTERFERENCE! But not so, for the machine I ran this on was directly wired via ethernet, and the airport is ethernet wired to the DSL termination equipment.

So it's the DSL right? Hold up - due to a weird quirk of putting the DSL CPE/router in bridge mode, I can still connect to it over wifi and get directly on my ISP's network (and get a public IP via DHCP). And when I do that with a different computer, BAM, performance is perfect.

So I hard power restart the Airport, and things maybe get better for a few minutes (if you can call 8 meg better - this is on a DSL line with 37 meg sync). Then nope, I am back to my 50 kB/sec downloads.

Anyone else see this? Am I just getting unlucky? The device is sitting on a cabinet, it has free airflow, it isnt being heated by anything else nearby, it's out of the direct sunlight, etc, etc. I can only assume that basically the hardware quality has gone to utter hell.

 

[jenzjen]

After you reset, leave wireless off connecting only via wired. Do your speeds stay fine over a long time frame or same degradation?

 

[ryanobjc]

After you reset, leave wireless off connecting only via wired. Do your speeds stay fine over a long time frame or same degradation?

I switched my airport to bridge mode, and made the DSL gateway do NAT again. Basically in short, when I'm on my airport, via either ethernet OR wifi (5GHz, transmit rate=450) I had similar 'speed test' results = 10 meg down and .4 meg up.

Switching my computer to directly use the DSL gateway, thus bypassing the Airport, I end up with a more respectable 15 meg down (probably limited by 2.4 ghz N) and more importantly a solid 2 meg up.

So it appears that it isnt related to NAT processing in the airport, but maybe it's some kind of switching issue? Not sure, I have reasonable cat6 patch cables hooking up the airport and the DSL gateway...

Just for reference, the network topology looks like thus:

INTERNETS (DSLAM/backhaul)
------------
DSL line termination unit
(includes: NAT, 4 port switch, 802.11n 2.4 GHz wifi)
--------
(cat6 patch cable)
--------
Airport Extreme/Timecapsule
(bridge mode, 802.11ac ,5/2.4 GHz)


From the airport, i have plugged in a desktop mac pro.

Here's the KILLER evidence, 2 pings, one to the airport (so just over 802.11), the other to the gateway, so over the SAME 802.11, then over 1 ethernet cable.

--- 192.168.1.12 ping statistics ---
20000 packets transmitted, 19995 packets received, 0.0% packet loss
round-trip min/avg/max/stddev = 0.559/1.109/11.950/0.473 ms

--- 192.168.1.1 ping statistics ---
20000 packets transmitted, 19299 packets received, 3.5% packet loss
round-trip min/avg/max/stddev = 1.057/2.097/14.850/0.610 ms

That's pretty brutal, 3.5% packet loss is huge. So the question is, what element is causing the problem now?

--- more

After switching cables around, it appears that there isnt a specific port issue - that is faulty switch port hardware is probably not to blame.

Being directly on the 802.11 provided by the DSL gateway, I get about 0.7% packet loss using the same methodology as above (ping -f -c 20000). I still need to try the same ping on ethernet to the DSL gateway to rule out the wireless network interference (I live in the city, and 2.4 can be congested).

It's still possible at this point that I have a flaky DSL gateway, or it might be the airport. I hope it's not the latter, because I've always found apple's network gear to be pretty reasonable, and not underpowered. I hope that hasnt changed.

 

[Macman45]

I use a first generation Time Capsule connected to a first generation AirPort Extreme and have no such issues.

If rebooting your modem doesn't help, make sure that wifi is only active on the TC and AE....if you've accidentally left wifi on in the ISP supplied router your issue could lie there. If not, I'd look closely at replacing the modem itself.

My speeds are constant and I have zero packet loss.

 

[jenzjen]

While possible, would be rare for two new TCs to exhibit the same issue unless something with your electrical causing issues - but then you would see it on other devices.

Do as other suggested, absolutely turn off wireless on your ISP modem and go from there.

 

[Altemose]

I switched my airport to bridge mode, and made the DSL gateway do NAT again. Basically in short, when I'm on my airport, via either ethernet OR wifi (5GHz, transmit rate=450) I had similar 'speed test' results = 10 meg down and .4 meg up.

Switching my computer to directly use the DSL gateway, thus bypassing the Airport, I end up with a more respectable 15 meg down (probably limited by 2.4 ghz N) and more importantly a solid 2 meg up.

So it appears that it isnt related to NAT processing in the airport, but maybe it's some kind of switching issue? Not sure, I have reasonable cat6 patch cables hooking up the airport and the DSL gateway...

Just for reference, the network topology looks like thus:

INTERNETS (DSLAM/backhaul)
------------
DSL line termination unit
(includes: NAT, 4 port switch, 802.11n 2.4 GHz wifi)
--------
(cat6 patch cable)
--------
Airport Extreme/Timecapsule
(bridge mode, 802.11ac ,5/2.4 GHz)


From the airport, i have plugged in a desktop mac pro.

Here's the KILLER evidence, 2 pings, one to the airport (so just over 802.11), the other to the gateway, so over the SAME 802.11, then over 1 ethernet cable.

--- 192.168.1.12 ping statistics ---
20000 packets transmitted, 19995 packets received, 0.0% packet loss
round-trip min/avg/max/stddev = 0.559/1.109/11.950/0.473 ms

--- 192.168.1.1 ping statistics ---
20000 packets transmitted, 19299 packets received, 3.5% packet loss
round-trip min/avg/max/stddev = 1.057/2.097/14.850/0.610 ms

That's pretty brutal, 3.5% packet loss is huge. So the question is, what element is causing the problem now?

--- more

After switching cables around, it appears that there isnt a specific port issue - that is faulty switch port hardware is probably not to blame.

Being directly on the 802.11 provided by the DSL gateway, I get about 0.7% packet loss using the same methodology as above (ping -f -c 20000). I still need to try the same ping on ethernet to the DSL gateway to rule out the wireless network interference (I live in the city, and 2.4 can be congested).

It's still possible at this point that I have a flaky DSL gateway, or it might be the airport. I hope it's not the latter, because I've always found apple's network gear to be pretty reasonable, and not underpowered. I hope that hasnt changed.

A good test here would be to connect an Ethernet cable to the DSL modem and try speed tests. Then try plugging the same cable to the AirPort's WAN port and resetting. Then via Ethernet off the AirPort, try another Speedtest.net test. If the result is lower via Ethernet off the AirPort than the off the Ethernet of the DSL modem then you have an issue. If it is the same then you have a bad DSL modem.

Perhaps I misunderstood, but the DSL modem was only tested via wireless, but the AirPort was tested via Ethernet and wireless. You want to test the DSL modem via Ethernet as well as I have seen some pretty bad LAN controllers on ISP supplied equipment.

 

[andrewthomas198]

Bridge mode is the problem

Never put the Time Capsule into bridge mode. Set to DHCP and NAT. If you get a double NAT message, click on it and hit ignore. Your wireless backups and speed can be affected if you put the TC in bridge mode. Time machine won't back up correctly if the TC is in bridge mode.

 

[priitv8]

Never put the Time Capsule into bridge mode. Set to DHCP and NAT. If you get a double NAT message, click on it and hit ignore. Your wireless backups and speed can be affected if you put the TC in bridge mode. Time machine won't back up correctly if the TC is in bridge mode.

How did you come to that conclusion?
I've run my TC in bridge mode from day 1 (it sits behind an AP Extreme in NAT mode) and I see no problems in network performance or backup reliability.

 

[laurihoefs]

Never put the Time Capsule into bridge mode. Set to DHCP and NAT. If you get a double NAT message, click on it and hit ignore. Your wireless backups and speed can be affected if you put the TC in bridge mode. Time machine won't back up correctly if the TC is in bridge mode.

Like priitv8 already asked, how'd you arrive to that conclusion?

I don't see any difference in backup speeds between bridge and NAT modes on a 4th gen. Time Capsule.
On the other hand, double NAT can cause issues, and Time Machine is not affected by bridge mode at all.

 

[Lennyvalentin]

Set to DHCP and NAT. If you get a double NAT message, click on it and hit ignore.

NO. Do not ignore double NAT messages, that means you have two DHCP servers on the same network trying to assign IPs to your devices. That is BAD and could cause networking problems. If you change your timecapsule from bridge to NAT, you should perform the reverse procedure on the broadband modem to correct the double NAT error.

To the original poster:
Have you investigated the influence of different wifi channels? If you run on 5GHz the risk of conflicts is greatly reduced compared to 2.4GHz band, but there might still be some other network tripping you up. ...This doesn't explain your issue with packet loss on wired ethernet though.