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ANSWERED In-tunnel upload speed issue with VPN on Ubuntu 14.04

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Hi everyone,


First of all, I have searched, but couldn't find anything matching my search terms. That may turn out to mean nothing, but yeah.


Anyway, I'm running AirVPN on a Desktop with Ubuntu 14.04. I'm located in Japan. I have a FTTH connection which is allegedly gigabit, but in practice ranges from 50 - 250mbps downstream and, on average, 50mbps upstream.


Anyway, I have an odd problem with the VPN service. When I do a speed test, I get some interesting results:


UK server, UDP, ports 443 and 53



Out-tunnel: 4.2mbps

In-tunnel: ~4mbps


Out-tunnel: ~15mpbs

In-tunnel: 0.45mbps


Singapore server, UDP, ports 443 and 53



Out-tunnel: ~18mbps

In-tunnel: ~18mbps


Out-tunnel: 12mbps

In-tunnel: 0.65mbps


Running a test on Speedtest.net gives similar results - the downstream bandwidth is fine, upstream bandwidth is not. The thing is, this upstream block just disappears when I run speedtest on the topen internet through their Japanese server. I get my 50mbps upload that I've always had. I even tried port 80 to see if my ISP is gaming speed tests. Bit Torrent works fine.


I've looked at the tutorials, and, like I said, I searched the forums. I'd appreciate any help anyone could give - this issue is basically preventing me from streaming (I think, unless the iPlayer issues discussed in other threads has not, in fact, been resolved). The thing is, streaming seems to work fine on my Android tablet with OpenVPN for Android installed.


Thanks in advance,



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I had a similar situation and eventually found the problem to be my Netgear N600 router was not compatible for the VPN.


Like you, download was fine but upload was non-existent. Once I got dd-wrt on my router, all was well.


On a side note, I found on my system I could temporarily work around the issue by patching a cable from the router to an ethernet switch I had laying around. To me more specific on the ethernet cabling arrangement:


modem out to ethernet switch > ethernet switch port (any) to router in > ethernet switch (any) to pc/newtwork card


This didn't come without a few negatives for me but it may work as a temporary solution if your issue matches my own. I don't really think it matters in this case but I'm on Kubuntu 14.04 as well, using openvpn.

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Thanks for the input!


My router uses DD-WRT by default, I think - it's a Buffalo WZR-450HP.


I've had my suspicions about it for a while regarding bandwidth available - I haven't had it very long, and it seems to refuse to negotiate the gigabit ethernet connection with the modem properly. Unfortunately the entire firmware is in Japanese and while I've been out here a while, my knowledge of the technical terms in Japanese is rather limited. One of the issues that has prevented me flashing an English firmware is the frequencies available for wi-fi in Japanese are different from the US (there are more channels available), and I don't want to brick the router.


I'll try with another router and see if that has any effect.


Thanks again!



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OK, it's a Japanese WZR-450HP, which basically means that Buffalo have gimped the router beyond salvation. I could install DD-WRT on it, but I'd have to open the case and solder a bloody serial port to the board!


However, in order not to be rash and stop myself potentially wasting money should I go out and drop some cash on a router unnecessarily, I'm going to try:


  • a direct connection between a PC and the modem, circumventing the router completely
  • wireless through the router.
  • turning off my wireless repeater
  • removing the switching hub in my office.

I mean, I enjoy spending money, but not on routers that I don't need.

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(This problem is "solved", not solved; I've started another thread asking for help that will properly fix the problem.)


I fixed it.


It turns out that the issue was basically caused by my being on a PPPoE connection (a common set-up for Japanese ISPs, particularly FTTH).


I found the solution here. The MTU size on my pipe is set to 1500, which, it seems, was "too large to fit into a UDP-in-PPPoE packet", and UDP can't adapt packet size.


To fix the problem, I dropped the MTU size on the client side (through the Ubuntu Network Manager > configure VPN > advanced) to 1270. Streaming has worked flawlessly ever since - no hangs, no drops and no unresponsive browsers that need to be force closed.

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