duplex negotiation

Discussion in 'Cisco' started by flamer die.spam@hotmail.com, Mar 19, 2007.

  1. flamer

    flamer Guest

    I have a link between a baystack switch and a cisco 1841 router, I
    have the
    same setup and same configuration at 70 other sites and have not seen
    this problem before.. when each device is manually set to 100/full the
    link goes down and I get no lights on either end, when one end is set
    to auto/auto and the other manually to 100/full the link comes up as
    100/full for anywhere between 10secs and several hours then drops back
    to half duplex. when both ends were auto auto they came up 100/half, I
    set
    the duplex on the switch only to full then the link was running 100/
    full, I tried manually setting the speed/duplex when the link was
    running correctly but that killed the link again and I couldn't get it
    running back at 100/full again.

    I have tried different switchports and it has the same problem, is it
    possible for a device to mis-report what duplex its running at? we are
    going to replace the cabling to ensure its not faulty but because it
    was able to run at full duplex it rules out a dodgy pair in the cable.

    at all the other sites we have 100/full statically set on the
    interfaces at each end.

    Flamer.
     
    flamer , Mar 19, 2007
    #1
    1. Advertising

  2. In article <>, "flamer " <> writes:
    [...]
    >I have tried different switchports and it has the same problem, is it
    >possible for a device to mis-report what duplex its running at?


    Yes, it is although this shouldn't be.

    >we are going to replace the cabling to ensure its not faulty but because it
    >was able to run at full duplex it rules out a dodgy pair in the cable.


    Not only the cable but as well the plugs could be the problem.

    >at all the other sites we have 100/full statically set on the
    >interfaces at each end.


    This should work. But I remember cases where devices from different brands or
    even different models from the same brand couldn't cope with each other.
    In addition, do your switches have the lastest software updates?

    Regards,
    Christoph Gartmann

    --
    Max-Planck-Institut fuer Phone : +49-761-5108-464 Fax: -452
    Immunbiologie
    Postfach 1169 Internet: gartmann@immunbio dot mpg dot de
    D-79011 Freiburg, Germany
    http://www.immunbio.mpg.de/home/menue.html
     
    Christoph Gartmann, Mar 20, 2007
    #2
    1. Advertising

  3. flamer

    Jim Allen Guest

    On 19 Mar 2007 16:04:19 -0700, "flamer "
    <> wrote:

    >I have a link between a baystack switch and a cisco 1841 router, I
    >have the
    >same setup and same configuration at 70 other sites and have not seen
    >this problem before.. when each device is manually set to 100/full the
    >link goes down and I get no lights on either end, when one end is set
    >to auto/auto and the other manually to 100/full the link comes up as
    >100/full for anywhere between 10secs and several hours then drops back
    >to half duplex. when both ends were auto auto they came up 100/half, I
    >set
    >the duplex on the switch only to full then the link was running 100/
    >full, I tried manually setting the speed/duplex when the link was
    >running correctly but that killed the link again and I couldn't get it
    >running back at 100/full again.
    >
    >I have tried different switchports and it has the same problem, is it
    >possible for a device to mis-report what duplex its running at? we are
    >going to replace the cabling to ensure its not faulty but because it
    >was able to run at full duplex it rules out a dodgy pair in the cable.
    >
    >at all the other sites we have 100/full statically set on the
    >interfaces at each end.
    >
    >Flamer.


    If one side of a connection is set to auto-negotiate and the other
    side to full duplex the auto-negotiate side will default to half
    duplex. Cisco recommends both sides of the link be set to
    auto-negotiation -

    Configuring and Troubleshooting Ethernet 10/100/1000Mb Half/Full
    Duplex Auto-Negotiation

    http://www.cisco.com/en/US/customer/tech/tk389/tk214/technologies_tech_note09186a0080094781.shtml

    If you manually set both sides to 100/full you need to watch the
    errors. If the wiring is inadequate your error rate can get quite
    high.

    - Jim
     
    Jim Allen, Mar 20, 2007
    #3
  4. flamer

    flamer Guest

    On Mar 20, 9:38 pm, Jim Allen <> wrote:
    > On 19 Mar 2007 16:04:19 -0700, "flamer "
    >
    >
    >
    > <> wrote:
    > >I have a link between a baystack switch and a cisco 1841 router, I
    > >have the
    > >same setup and same configuration at 70 other sites and have not seen
    > >this problem before.. when each device is manually set to 100/full the
    > >link goes down and I get no lights on either end, when one end is set
    > >to auto/auto and the other manually to 100/full the link comes up as
    > >100/full for anywhere between 10secs and several hours then drops back
    > >to half duplex. when both ends were auto auto they came up 100/half, I
    > >set
    > >the duplex on the switch only to full then the link was running 100/
    > >full, I tried manually setting the speed/duplex when the link was
    > >running correctly but that killed the link again and I couldn't get it
    > >running back at 100/full again.

    >
    > >I have tried different switchports and it has the same problem, is it
    > >possible for a device to mis-report what duplex its running at? we are
    > >going to replace the cabling to ensure its not faulty but because it
    > >was able to run at full duplex it rules out a dodgy pair in the cable.

    >
    > >at all the other sites we have 100/full statically set on the
    > >interfaces at each end.

    >
    > >Flamer.

    >
    > If one side of a connection is set to auto-negotiate and the other
    > side to full duplex the auto-negotiate side will default to half
    > duplex. Cisco recommends both sides of the link be set to
    > auto-negotiation -
    >
    > Configuring and Troubleshooting Ethernet 10/100/1000Mb Half/Full
    > Duplex Auto-Negotiation
    >
    > http://www.cisco.com/en/US/customer/tech/tk389/tk214/technologies_tec...
    >
    > If you manually set both sides to 100/full you need to watch the
    > errors. If the wiring is inadequate your error rate can get quite
    > high.
    >
    > - Jim


    Thanks for the advice both of you, I am thinking now that perhaps the
    devices never really were running at full-duplex and the cable may
    need replacing, although on the cisco it was reporting full duplex and
    no errors for a while now it half duplex it has many errors and resets
    on the interface. I know there have always been auto neg issues with
    cisco in the past but all the routers and switches are running the
    same ios versions and have the same config and everything so its just
    one site that isn't working correctly. should i try set the port
    duplex/speed without the cable plugged in maybe?

    Flamer.
     
    flamer , Mar 20, 2007
    #4
  5. flamer

    none Guest

    On Tue, 20 Mar 2007 09:38:12 +0000, Jim Allen wrote:

    > Cisco recommends both sides of the link be set to auto-negotiation -


    The article on the Cisco site you quoted says different...

    "Both sides of a link should have auto-negotiation on, or both sides
    should have it off. Cisco recommends to leave auto-negotiation on for
    those devices compliant with 802.3u."
     
    none, Mar 22, 2007
    #5
  6. flamer

    Guest

    On 22 Mar, 00:24, none <> wrote:
    > On Tue, 20 Mar 2007 09:38:12 +0000, Jim Allen wrote:
    > > Cisco recommends both sides of the link be set to auto-negotiation -

    >
    > The article on the Cisco site you quoted says different...
    >
    > "Both sides of a link should have auto-negotiation on, or both sides
    > should have it off. Cisco recommends to leave auto-negotiation on for
    > those devices compliant with 802.3u."


    Autonegotiation is almost always superior to any manual
    fiddling - as a general statement.

    This issue feels like a bad cable. With FD there are greater
    demands on the cable since both ends may be transmitting
    at the same time. This means that the receiver has to be
    able to cope with its own transmitter blasting out with
    orders of magnitude more power than the expected
    received signal. To make this work you need a
    proper cable.

    Bear this in mind - autonegotion is good.

    More networking problems have been caused by
    misguided manual intervention in this area
    than have ever been fixed by it.

    Read the current Cisco advice and believe it.
    If it's not working as advertised something is broken.

    Until a few years ago I NEVER trusted the duplex
    setting reported. Trust ONLY the error counters
    on networking equipment that you trust. I you
    have old kit then suspect the settings reported.
     
    , Mar 22, 2007
    #6
  7. flamer

    flamer Guest

    On Mar 22, 1:14 pm, wrote:
    > On 22 Mar, 00:24, none <> wrote:
    >
    > > On Tue, 20 Mar 2007 09:38:12 +0000, Jim Allen wrote:
    > > > Cisco recommends both sides of the link be set to auto-negotiation -

    >
    > > The article on the Cisco site you quoted says different...

    >
    > > "Both sides of a link should have auto-negotiation on, or both sides
    > > should have it off. Cisco recommends to leave auto-negotiation on for
    > > those devices compliant with 802.3u."

    >
    > Autonegotiation is almost always superior to any manual
    > fiddling - as a general statement.
    >
    > This issue feels like a bad cable. With FD there are greater
    > demands on the cable since both ends may be transmitting
    > at the same time. This means that the receiver has to be
    > able to cope with its own transmitter blasting out with
    > orders of magnitude more power than the expected
    > received signal. To make this work you need a
    > proper cable.
    >
    > Bear this in mind - autonegotion is good.
    >
    > More networking problems have been caused by
    > misguided manual intervention in this area
    > than have ever been fixed by it.
    >
    > Read the current Cisco advice and believe it.
    > If it's not working as advertised something is broken.
    >
    > Until a few years ago I NEVER trusted the duplex
    > setting reported. Trust ONLY the error counters
    > on networking equipment that you trust. I you
    > have old kit then suspect the settings reported.


    the work we did yesterday seemed to go well, we had to use a straight
    through cable (cat5e which is more than adequate for 100mb/fd) and
    strapped both sides manually o 100/full the link stayed stable and
    had no errors or collisions reported.. I kept a watch on the counters
    for 25mins and stayed running fine I have to check again today to see
    if its still running fd with no errors.. I can't see why it wouldn't..
    cross-over cable still immediately killed the link..

    Flamer.
     
    flamer , Mar 22, 2007
    #7
    1. Advertising

Want to reply to this thread or ask your own question?

It takes just 2 minutes to sign up (and it's free!). Just click the sign up button to choose a username and then you can ask your own questions on the forum.
Similar Threads
  1. AP/Client connection negotiation process.

    , Aug 9, 2005, in forum: Wireless Networking
    Replies:
    3
    Views:
    684
    Pavel A.
    Aug 10, 2005
  2. Bill F
    Replies:
    0
    Views:
    666
    Bill F
    Nov 2, 2003
  3. Mark
    Replies:
    12
    Views:
    5,132
    yeah!
    Jan 22, 2004
  4. Greg Oleksiak
    Replies:
    2
    Views:
    1,332
    Greg Oleksiak
    May 3, 2004
  5. DigitalSierra

    ECP Half-duplex or Full-Duplex?

    DigitalSierra, Oct 18, 2004, in forum: A+ Certification
    Replies:
    0
    Views:
    647
    DigitalSierra
    Oct 18, 2004
Loading...

Share This Page