Strange Network Behaviour - Next Installment - Debian

This is a discussion on Strange Network Behaviour - Next Installment - Debian ; This is to keep informed Bit Twister and others who were following the previous thread. To recap: LAN -> switch-> linux gateway/router -> DMZ -> ADSL2-modem/router Hosts on the lan sometimes cannot see the gateway and beyond. Rather than try ...

+ Reply to Thread
Results 1 to 11 of 11

Thread: Strange Network Behaviour - Next Installment

  1. Strange Network Behaviour - Next Installment


    This is to keep informed Bit Twister and others who were following the
    previous thread. To recap:

    LAN -> switch-> linux gateway/router -> DMZ -> ADSL2-modem/router

    Hosts on the lan sometimes cannot see the gateway and beyond.


    Rather than try to quantify the throughput of the linux gateway box, I
    replaced it with something with considerable more grunt. I ended up using
    a Celery 3 GHz machine, and still had the problems. So I'm pretty sure
    that it's not a throughput problem, although it never really looked
    like one anyway. I can see throughput slowing the network down, but not
    making the gateway invisible.

    So the problem appears to be the switch, but this was the first thing I
    replaced ages ago.

    So now I've added a second gateway box and routed everything from
    downstairs through it. Upstairs and downstairs are now effectively
    isolated. Both their gateways go onto the dmz and from there out to the
    internet. I've got my ping diagnostics that Bit Twister recommended
    running on boxes on both parts of the network. Now to see if, when, and
    where errors occur.

    Dan


  2. Re: Strange Network Behaviour - Next Installment

    "Dan N" wrote in message
    newsan.2006.05.10.07.20.46.561206@localhost.localdomai n

    > This is to keep informed Bit Twister and others who were following the
    > previous thread.


    Too bad you started a new thread, as the historical connection will be lost
    to those who need it in the future.


  3. Re: Strange Network Behaviour - Next Installment

    On Wed, 10 May 2006 15:20:50 +0800, Dan N wrote:

    > This is to keep informed Bit Twister and others who were following the
    > previous thread.


    I was wondering if I had somehow missed a post or two...

    > Rather than try to quantify the throughput of the linux gateway box, I
    > replaced it with something with considerable more grunt. I ended up using
    > a Celery 3 GHz machine, and still had the problems. So I'm pretty sure
    > that it's not a throughput problem, although it never really looked
    > like one anyway.
    > I can see throughput slowing the network down, but not
    > making the gateway invisible.


    I thought so also. I had seen someone mention a 10mb nic could be kept
    maxed out with an old pokey 486 a few years ago.

    Your system should have been able to keep up due to throttling at the
    internet connection.

    The only thing I could dream up would be a lan side gateway firewall thinking
    it need to throttle inbound. I just would not believe it.


    > So the problem appears to be the switch, but this was the first thing I
    > replaced ages ago.


    I was guessing the switch, but as a victim, the culprit being the doze
    boxes beating up the network causing collisions. That still did not
    make sense because I would think pings should still get through.

    > So now I've added a second gateway box and routed everything from
    > downstairs through it. Upstairs and downstairs are now effectively
    > isolated.


    Well that knocks off the load/collisions at the switch.

    Upside is you can stop the ping test and watch the tx/x counts on each
    lan gateway nic and see if you have very high traffic conditions.

  4. Re: Strange Network Behaviour - Next Installment

    On Wed, 10 May 2006 00:28:38 -0700, ynotssor wrote:

    > Too bad you started a new thread, as the historical connection will be
    > lost to those who need it in the future.


    The alternative was to use an old thread that might have gone out of view.

    Dan


  5. Re: Strange Network Behaviour - Next Installment

    On Wed, 10 May 2006 03:28:29 -0500, Bit Twister wrote:

    >> So the problem appears to be the switch, but this was the first thing I
    >> replaced ages ago.

    >
    > I was guessing the switch, but as a victim, the culprit being the doze
    > boxes beating up the network causing collisions. That still did not make
    > sense because I would think pings should still get through.


    None of it makes any real sense. I'm thinking there might be some kind of
    hardware issue. I want to say something like different earth levels, but
    ethernet is differential signals not referenced to ground, so that can't
    be right. But something along those lines. It can be solid for a couple
    of days, then have ping errors every five minutes all day. And sometimes
    it looks like it's related to the hours when there's more traffic, but
    other times it happens in the middle of the night.

    Since I've separated the network, each with its own gateway, it's been
    solid. But I need to watch it at least a couple of days.

    Dan



  6. Re: Strange Network Behaviour - Next Installment

    "Dan N" wrote in message
    newsan.2006.05.10.11.02.54.702704@localhost.localdomai n

    >> Too bad you started a new thread, as the historical connection will
    >> be lost to those who need it in the future.

    >
    > The alternative was to use an old thread that might have gone out of
    > view.


    What does "gone out of view" mean?

  7. Re: Strange Network Behaviour - Next Installment

    On Wed, 10 May 2006 12:27:28 -0700, ynotssor wrote:


    > What does "gone out of view" mean?


    Means you can't see it anymore because new posts push it down the list.
    Means it can go unnoticed.


  8. Re: Strange Network Behaviour - Next Installment

    On Wed, 10 May 2006 15:20:50 +0800, Dan N wrote:

    Here's the latest. Upstairs shows no ping errors. Downstairs is pinging
    its gateway plus hosts in the dmz. All is well, except that it's missing
    the odd ping to the mail server in the dmz, which is a bit odd. Before I
    installed the second gateway, ping errors occurred to the gateway. Now
    they're occurring with only one host in the dmz.

    Dan



    > This is to keep informed Bit Twister and others who were following the
    > previous thread. To recap:
    >
    > LAN -> switch-> linux gateway/router -> DMZ -> ADSL2-modem/router
    >
    > Hosts on the lan sometimes cannot see the gateway and beyond.
    >
    >
    > Rather than try to quantify the throughput of the linux gateway box, I
    > replaced it with something with considerable more grunt. I ended up using
    > a Celery 3 GHz machine, and still had the problems. So I'm pretty sure
    > that it's not a throughput problem, although it never really looked like
    > one anyway. I can see throughput slowing the network down, but not making
    > the gateway invisible.
    >
    > So the problem appears to be the switch, but this was the first thing I
    > replaced ages ago.
    >
    > So now I've added a second gateway box and routed everything from
    > downstairs through it. Upstairs and downstairs are now effectively
    > isolated. Both their gateways go onto the dmz and from there out to the
    > internet. I've got my ping diagnostics that Bit Twister recommended
    > running on boxes on both parts of the network. Now to see if, when, and
    > where errors occur.
    >
    > Dan



  9. Re: Strange Network Behaviour - Next Installment

    On Thu, 11 May 2006 10:40:57 +0800, Dan N wrote:
    > On Wed, 10 May 2006 15:20:50 +0800, Dan N wrote:
    >
    > Here's the latest. Upstairs shows no ping errors. Downstairs is pinging
    > its gateway plus hosts in the dmz. All is well, except that it's missing
    > the odd ping to the mail server in the dmz, which is a bit odd. Before I
    > installed the second gateway, ping errors occurred to the gateway. Now
    > they're occurring with only one host in the dmz.


    Rule out the switch by swapping up upstair switch with downstair switch.
    Or gateway box whichever is common.
    No change, swap downstair lan boxes with upstairs lan boxes.

  10. Re: Strange Network Behaviour - Next Installment

    "Dan N" wrote in message
    newsan.2006.05.11.01.30.45.700306@localhost.localdomai n

    >> What does "gone out of view" mean?

    >
    > Means you can't see it anymore because new posts push it down the
    > list. Means it can go unnoticed.


    How absurd ... learn to take control of your Pan newsreader:

    Filter -> [uncheck] Match Read Articles

  11. Re: Strange Network Behaviour - Next Installment

    On Wed, 10 May 2006 21:59:10 -0500, Bit Twister wrote:

    > Rule out the switch by swapping up upstair switch with downstair switch.
    > Or gateway box whichever is common.
    > No change, swap downstair lan boxes with upstairs lan boxes.


    I've also now got a couple of ping errors on the other part of the network
    going through the original gateway. And also only to selected hosts in
    the dmz. So the behaviour is different to before, but the same on both
    segments of the network.

    But no-one has reported any outages!

    This is what I think is happening. There's some kind of impedance
    miss-match or similar that's causing signal reflections or other timing
    errors. The switch sees this and stumbles, and we see it on the port with
    the highest traffic, the one going to the gateway. There's a single cable
    that goes from upstairs to a downstairs switch, and it has a join in it,
    one of those cat5 couplers. I've ordered a new roll of cable and will
    replace this and some others that I think are suspect. I'll also run some
    more cables downstairs so all the traffic doesn't go on the one. I'll also
    tidy up the spaghetti of cables between the patch panel and the switch.

    I'm not sure why I'm losing very occasional pings on selected hosts
    in the dmz though. But it doesn't seem to be causing a problem anywhere.

    Dan





+ Reply to Thread