PPPOE disconnection with high uploads

evb Posts: 2
First Comment
edited April 2021 in Security

First maybe some information about the installation:
- a vdsl modem bbox3 from my ISP provider Proximus (Belgium)
- Connected to this modem a Zywall 110, building his own PPPOE connection through the modem.

The installation worked for years without a problem with a bbox2.
In the beginning of the year Proximus did change the bbox2 by a new bbox3.
Everything was still working fine.
After some time, I think August, users started complaining about 'no internet' connection, so I did some tests and saw that a high upload like for example a big file upload using WeTransfer, did drop the PPPOE connection.
In the log file of the Zywall I saw following occurring each 2 minutes during the upload:

Did my ISP drop the connection?
So I contacted them and they did see the following in their Radius logs:

So their conclusion, the Zywall was requesting a termination of the connection...

I did check my PPOE configuration: 

This configuration did work for years, so what is the problem?
I'm using the latest firmware

So, I did some extra tests.
In my backup software I can limit the upload rate of a cloud account. So I configured as test a sync of a big file to the cloud.
So first I did try with unlimited upload : bingo, each 2 minutes a PPPOE drop and auto reconnection by the Zywall.
So, I throttled down the speed upload and by trial and error I found that limiting to 500kpbs did not drop the PPPOE connection.

Okay, but what now?
I have two parameters that changed here, a change of modem model from bbox2 to bbox3 and firmware updates of the Zywall.
Is there a problem in the firmware of the Zywall, a problem in the bbox3, I don't know.
What can I do more as tests?


All Replies

  • Alfonso
    Alfonso Posts: 257  Master Member
    First Anniversary Friend Collector First Answer First Comment
    Hi @evb

    Welcome to the forum.

    I agree your situation is very frustrating. And unlikely I do not have the magic wand to solve your issue.

    I  recommend to read the following post, you maybe get complementary information 


  • evb
    evb Posts: 2
    First Comment
    Hi @Alfonso
    Thanks for the information.
    I don't think that the case described in the article, can be the one causing my problems.
    In normal conditions (=normal surfing on the web) + downloading big files + VPN connections, I don't have PPPOE disconnections.
    The PPPOE disconnection occurs only if uploading big files.
    Meanwhile I've done another test by throttling the egress bandwidth of the Zywall to the real number of Kbps of the ISP, but no luck, stil PPPOE disconnection when uploading big files.

    I see that I have stil the old previous firmware as standby backup in the Zywall.
    I hesitate to downgrade, because I don't want to lose my configuration rules.
    This is a working prod environment, so I must be carefully.
    I will see if I find information about downgrading and the related dangers.

  • Zyxel_Emily
    Zyxel_Emily Posts: 1,296  Zyxel Employee
    First Anniversary 10 Comments Friend Collector First Answer
    Hi @evb,

    If the issue "PPPoE disconnection when uploading big files" happens again, please help us collect packets on PPPoE interface to find out the root cause.

    When the issue happens again, 
    1. Go to MAINTENANCE > Diagnostics > Packet Capture. Move ppp interface to "Capture Interfaces" and click "Capture" to start collecting packets for a while. Click "Stop" and download the captured file.

    2. Send captured packet file to us via private message for analysis.

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