Diagnosing PPP errors

Discussion in 'Tomato Firmware' started by scottlindner, Jul 12, 2009.

  1. scottlindner

    scottlindner Addicted to LI Member

    I have been using Tomato for a while and absolutely love it. I recently changed to a new DSL account. Nothing changed physically, just my DSL telephone number and PPP credentials. The reason was to get dry loop DSL so I could dump my phone line and port the number to Ooma. After switching to the new DSL account I get frequent (1-4 times per day) disconnects with an LCP error. I have contacted question several times but they say nothing is wrong. Are there any tools available to help me dig deeper into this?

  2. Planiwa

    Planiwa Network Guru Member

    You want to achieve clarity about whether you (also) lose sync when you lose PPP.
    Your modem has that information.

    If you lose sync, your problem is not a PPP problem. Otherwise, good luck! :)

    Here is a secret for you:

    nvram get ppp_get_ac # this identifies your Access Concentrator.

    nvram get wan_gateway # this identifies your wan gateway.
  3. scottlindner

    scottlindner Addicted to LI Member

    Unfortunately my modem does not have any logs at all. It has some physical information such as SNR, but that's about it. If there are logs, I haven't found them yet. I have the ActionTec M1000 (provided by QWest) if that helps.

    How do those two parameters help me?

  4. Planiwa

    Planiwa Network Guru Member

    Modems often have DSL uptime, or number of DSL resets, or even # of superframes, or # ATM cells.

    All of these can be used to determine if a recent PPP reset was associated with a DSL resync.

    If it turns out that there was no DSL sync, then knowing which AC and which WAN gateway (along with which WAN IP address) will be helpful when talking with your ISP.

    In the Tomato log you will see one of two messages:

    "Received LCP termination request" -- this means that the AC (or your modem!) asked (demanded) that the PPP session be terminated.

    "LCP appears to be disconnected" -- this means that the PPP session was not properly terminated.
  5. scottlindner

    scottlindner Addicted to LI Member

    Thanks. I will note those two pieces of information, and start periodically checking the modem stats so I can see what changes after the next disconnect.

    "LCP appears to be disconnected" is the error that I am receiving. Does that mean anything to you?

    Thank you for all of this. I have been searching and reading tons of forums for nearly a month and haven't made any progress. You have provided some of the best technical information so far.

  6. occamsrazor

    occamsrazor Network Guru Member

  7. scottlindner

    scottlindner Addicted to LI Member

    I am using an ActionTec M1000 configured in a fully bridged mode.

    I read your sample log of errors. That is not the situation I am having. I plan to read your thread in case I might learn something to help me diagnose the problem. Thanks for sharing!

  8. scottlindner

    scottlindner Addicted to LI Member

    I know this isn't a DSL forum but I am hoping someone might be able to help. I configured my DSL router as a router (took it out of bridging) and have my Tomato router behind it in a double NAT, double port forwarding configuration. I did this so I could see the detailed status of my DSL connection. I had another disconnect and the data on my DSL modem didn't change. No errors at all. Not even an authentication error. Totally perfect DSL service.

    So based on this and my previous LCP appears to be disconnecting (pending 5) error when using Tomato, does anyone have any ideas as to what might be going on so I have better information when I call QWest tech support?

  9. Planiwa

    Planiwa Network Guru Member

    Take a look at:


    Get your Line Stats from the modem.
    Be clear about what "resync" means.
    Be clear about what a PPP session is.

    Be clear about whether one or the other or none "disconnects"

    Also, be clear that any "slowdowns" could be due to customer site (tracked connection surges), or network congestion.

    If there are no resyncs, it is extremely unlikely that it is a DSL problem.
  10. scottlindner

    scottlindner Addicted to LI Member

    There are no retrains. I am assuming this is a "resync".

    From other threads I have read it sounds like it isn't DSL, but something with the LCP authentication being terminated without a reason at QWest. I haven't changed anything but my DSL account. Just the username and password changed. Prior to the DSL account change I never had this problem, after it I have an LCP disconnect about every 24 hours but the time of day appears to be random.

    Does anyone know if Tomato can report the LCP error codes as described in the following link?

    I disconnected again this morning while working from home. Note there are zero physical errors such as FEC or CRC. There are no authentication errors, but the session timer restarted and I was issued a new IP.
    I snagged this from the DSL modems log file:
    Again, I know this isn't a DSL forum and I am cross posting similar information on a DSL forum. BUT, if I can get better debug information from Tomato to help me resolve this I'd appreciate it. Is there a way to enable more verbose error details to see what's going on with the LCP?

  11. Planiwa

    Planiwa Network Guru Member

    Seems to me that you don't have a DSL problem, you have a PPP problem.

    If you let your router do PPP, then you have a "Tomato Situation". :)

    In any case, you could use tcpdump, if you really want to to trace what happens.

    Here is a secret:

    1. Leave your modem set up to do PPP ("routed mode").
    2. Set your router up for PPP through the modem. (what? I can do that?).
    3. Monitor your 2 PPP sessions, and see if the failures are synchronised.

    That will give you an additional clue about what might be going on.
    Also, see if the PPP disconnects are on a schedule.

    Try to determine whether other users have problems with the same Access Concentrator / Edge Router.

    (If you use MS, perhaps RASPPPOE gives better diags?)
  12. scottlindner

    scottlindner Addicted to LI Member

    Good suggestion. If they are synchronized that tells me a lot.

    Do you happen to know if I can get the error code? That would help as well.

  13. scottlindner

    scottlindner Addicted to LI Member

    I got the problem sorted out. It was a problem on QWest's end and was not related to anything within my environment. You better believe they wouldn't accept that each time I called them about it though. They blamed Microsoft, IE, A/V software, wireless disconnections (I don't use wireless), and of course they blamed Tomato. What they never suggested was "Oh my gosh, we might have a problem to investigate"

    I don't know what the problem was. They ran a series of tests that spanned an hour and since those tests the problem went away. One person suspects they rebooted something which sucked in my new account settings.

    You can read about it here if you're interested: http://www.dslreports.com/forum/r22763835-frequent-disconnects

    Thanks for the help!

  14. Planiwa

    Planiwa Network Guru Member

    The AC which handles PPP is not necessarily anywhere near the DSLAM. It could be several hundred km away. Bell Canada i known to block PPP login attempts that "look like intrusions". Tomato resending PADI's at 5s intervals sure looks like instrusion attempts to some. There is lots of buiggy software out there, and all sorts of things that can go wrong, with PPP authentication.

    The main reason to learn to understand PPP logs is to demonstrate that the problem is not with the user. :) (Unless it's a password typo, which is easy to eliminate.)

    Bell Canada uses IKNS (Ikanos) DSLAMs with known bugs. Perhaps it's more important to deploy DPI "functionality" than to fix basic DSL integrity problems.
  15. scottlindner

    scottlindner Addicted to LI Member

    What is DPI?
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