1700 series: S0 is up 2 hours, down 2 hours, up, down, arghgh!

Discussion in 'Cisco' started by Ivan, Oct 12, 2004.

  1. Ivan

    Ivan Guest

    Anyone ever seen this? Two 1750s; serial 0/0 are CSU/DSU WICs
    connected over a leased T1 line. I do a 'show log' and see that the
    line goes down 2hrs, and almost exactly 2hrs later, I see it comes up.
    And stays up 2hrs, goes down. Down 2hrs, back up. Over and over. When
    its up everything works fine, no errors on the interface at all. When
    its down, a 'show int s 0/0' shows that the line is up, protocol down.

    Are there any settings that I could have messed up that would cause
    this? I have a *really* basic config on these. They have the Firewall
    image, but I haven't even enabled it yet. Just a couple of routers
    using HDLC and TCP/IP. Using static default routes. The T1 uses ESF
    and B8ZS.

    I suspect the Telco, but since they claim they can loop the
    smartjacks, I'm SOL with them.

    Appreciate any advice you can offer.
    Ivan, Oct 12, 2004
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  2. Ivan

    Ben Guest

    Could well be a clocking problem...the interface is cycling in and out of
    being in sync with the provider.

    Check whether your provider is supposed to provide clocking or if you are
    supposed to clock internally on the type of service you have.

    With line clocking ("clock source line" under the controller) both routers
    get a signal from the telco.

    With internal clocking ("clock source internal") only one of the routers has
    to be configured this way as it will then transmit the clock signal on the

    By the way not sure if your WIC has a T1 controller. If not the config may
    be under the serial interface itself and the commands may differ a little
    (transmit-clock-source? from memory)
    Ben, Oct 12, 2004
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  3. Ivan

    dmcknigh Guest

    You may want to look at the clocking. If your deriving clock from the
    circuit, it will be harder to track down a clocking problem, but it
    can be done (using a T-Berd or similar diagnostic device). Another
    possibility would be some kind of memory leak issue, but I seriously
    doubt that you would see the kind of regular interface cycling that
    your experiencing with a memory leak.
    HTH, David
    dmcknigh, Oct 12, 2004
  4. Ivan

    AnyBody43 Guest

    I am not complaining about Ben's response AT ALL. Indeed it
    seems a fine plan.

    This however seems intriguing.

    2 x 1.5 Mhz clocks drifting by 1 cycle every 4 hours.

    That is a rate of 1 second in 700 years.
    Hmmmm - when did Cisco start fitting Atomic clocks to the kit?

    Oh no!
    They seem to do even better, http://whyfiles.org/078time/2.html -
    "To put it another way, this clock will stay within one second of
    true time for 6 million years"

    Well it seems it might be true.
    "The NIST program on chip-scale atomic clocks" seems to have EXACTLY
    the right accuracy:)
    AnyBody43, Oct 12, 2004
  5. Ivan

    Ivan Guest

    Thanks for the replies. I meant to include the fact that I am doing
    the internal clocking on one of the routers and that I had double
    checked that.

    I ended up calling the Telco on their bluff and their dire warnings
    that I would be charged if they had to come out and the problem was on
    my end. They came out, fiddled around, had someone at the CO fiddle
    around, and when they were done the line came up and has stayed up (so
    far). They never really came out and said how they fixed it. I'm not
    sure they really know.
    Ivan, Oct 12, 2004
  6. That's been pretty much the characteristic of the Telcos.
    They don't want to admit it is their problem and they don't want to
    make a trip out when they can scare you into thinking that you might
    be charged for the trip.

    More times than not, it is their problem. Rarely is their a
    wiring problem on your end. If it is a customer equipment problem,
    then you should have checked all of your equipment before calling

    I've actually had times when they said there was no problem on
    the line but miraculously everything that wasn't working before they
    looked at it is now working. Coincidence? Hardly.

    I think that they think they will be shot if something is
    wrong with their equipment.

    Fred Atkinson, Oct 13, 2004
  7. *snort* you too? :) "honestly, no-one touched ANYTHING for your line
    and now it's working? it's a miracle!!!"
    Dan Swartzendruber, Oct 13, 2004
  8. Isn't that a famous quote from "The Shawshank Redemption"? I
    think it's what the warden said when he didn't know how Andy had
    escaped from his cell. ;-)


    Fred Atkinson, Oct 13, 2004
  9. :) I was always amused by trying to guess how long it would be after
    opening a ticket with Bell Atlantic before the T1 (which had been down
    for hours) would magically heal itself...
    Dan Swartzendruber, Oct 13, 2004
  10. I can see that we've both had the same experiences.

    I used to be Telco support (among my other functions) for
    SkyTel Technical Operations. We used data and dialup lines from all
    over the country. I interfaced with many different telephone
    companies all over the country.

    Sometimes they'd try to snow me. Sometimes I escalated
    through them internally. On rare occasion, I called whichever state's
    Public Service Commission was appropriate. But, I always got it
    resolved when no one else could. But if we had to rely on those
    Telcos, a lot of problems wouldn't have gotten resolved by itself.

    When I worked for MCI, one of my later specialties was
    interfacing with troubled accounts. When they sent me over to fix
    someone's WATS or data lines, it was generally because those customers
    were ready to eat the next representative of our company alive.
    Didn't bother me, though. I always had them eating out of my hand
    before I left. And I rammed heads with Telco field personnel more
    times than I wish I had had to. It only took a few times where they
    told me there was no problem on the line and I proved them wrong
    before they had a chance to regroup. Sometimes, I fixed their
    equipment myself.

    After I started making them look so bad, the Telco field guys
    got the word about me. After that, when I encountered them and asked
    them to do something, it was 'Yes, sir' with no argument. They did
    it, too.

    Good to bump into someone with similar experiences.

    Fred Atkinson, Oct 13, 2004
  11. Ivan

    Ben Guest

    Wow, I thought that was just the big T out here in Australia that pulled
    that trick!
    Ben, Oct 14, 2004
  12. Ivan

    Velvet Guest

    Happens in the UK a lot too. BT are notorious for it. Frequently I
    call a fault in to them, half an hour later, line pops up, runs fine,
    they say no fault found...

    Probing over the years has led to a few of them telling me the automated
    line check they do can reset something which will bring the line up.
    I've no idea if it's true - if it is then they should see historically
    something's been tripped, but they never admit to anything.
    Velvet, Oct 14, 2004
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