Is this normal for a 2600 router?

Discussion in 'Cisco' started by Michael Love, Apr 8, 2004.

  1. Michael Love

    Michael Love Guest

    We have a Cisco 2600 router at our office that we've been using for about 4
    years. It is running IOS Version 12.0(7)T3. It connects our network to the
    internet with a T1.

    Last night while checking over its configuration, I saw that FastEthernet
    0/0 was manually set to 100mbps half-duplex. It is plugged into a 100mbps
    full-duplex switch. Thinking this was odd, I switched to auto-sense and it
    picked up as 100mpbs full-duplex. I thought everything was ok until I came
    in today and saw that our monitoring software was reporting packet loss to
    the router. Other devices plugged into that switch are correctly
    auto-detecting and aren't having problems.

    Well, I did some testing, replacing the switch and cabling and got the
    following results:
    Our router is called "cisco1" and our gateway machine is called "thing1".
    "Cisco2" is a new 2600 router we just had installed so we can provide DSL
    service to our customers. Cisco2 is connected to the eth4 interface in
    thing1 via a crossover cable. Thing1 is a 1u rack-mounted PC that runs our
    firewall and connects our local subnets together. It has a built-in nic that
    is set to eth0 and connects it to our server network. Its also has a 4-port
    ethernet card that Cisco1 and Cisco2 are connected on separate ports.

    1) I did a ping flood test of "ping -f -c 5000 cisco1" and I lose about
    30-40 packets everytime.
    2) I lose no packets if the interface is forced to half duplex
    3) I replaced the switch and still get the same results
    4) I replaced the cabling and still get the same results
    5) I plugged thing1 directly into cisco1 with a crossover cable and get the
    same results
    6) I do not get these results when pinging cisco2's fastethernet interface
    with the same command. It is at full duplex with 0 loss.

    This leads me to believe either:
    1) There is a problem with thing1's eth1 interface. It is a machine we just
    connected recently, a clone of the older one, and we extensively tested the
    ethernet ports for a week beforehand.
    2) There is a problem in cisco1's FastEthernet interface.
    3) There is a reason that the interface was manually set to half-duplex that
    I don't understand. Neither of the other technicians, or the owner who
    installed the unit, know why it was forced to half in the first place,
    though.

    I am not a master of Cisco equipment. Although I'm familiar with networking
    and network troubleshooting, I've only really been responsible for the Cisco
    IOS equipment in the last year and have been reading books on how to use
    IOS.

    Does this sound like a problem in either of the units above, or is there
    some specific reason that the interface should be set to half-duplex that
    I'm missing or don't understand?

    ---------------------------
    Michael Love,
    SDC Technical Support
    http://www.sdc.org
    Michael Love, Apr 8, 2004
    #1
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  2. Michael Love

    Rik Bain Guest

    On Thu, 08 Apr 2004 17:28:40 -0500, Michael Love wrote:

    > We have a Cisco 2600 router at our office that we've been using for
    > about 4 years. It is running IOS Version 12.0(7)T3. It connects our
    > network to the internet with a T1.
    >
    > Last night while checking over its configuration, I saw that
    > FastEthernet 0/0 was manually set to 100mbps half-duplex. It is plugged
    > into a 100mbps full-duplex switch. Thinking this was odd, I switched to
    > auto-sense and it picked up as 100mpbs full-duplex. I thought everything
    > was ok until I came in today and saw that our monitoring software was
    > reporting packet loss to the router. Other devices plugged into that
    > switch are correctly auto-detecting and aren't having problems.
    >
    > Well, I did some testing, replacing the switch and cabling and got the
    > following results:
    > Our router is called "cisco1" and our gateway machine is called
    > "thing1". "Cisco2" is a new 2600 router we just had installed so we can
    > provide DSL service to our customers. Cisco2 is connected to the eth4
    > interface in thing1 via a crossover cable. Thing1 is a 1u rack-mounted
    > PC that runs our firewall and connects our local subnets together. It
    > has a built-in nic that is set to eth0 and connects it to our server
    > network. Its also has a 4-port ethernet card that Cisco1 and Cisco2 are
    > connected on separate ports.
    >
    > 1) I did a ping flood test of "ping -f -c 5000 cisco1" and I lose about
    > 30-40 packets everytime.
    > 2) I lose no packets if the interface is forced to half duplex 3) I
    > replaced the switch and still get the same results 4) I replaced the
    > cabling and still get the same results 5) I plugged thing1 directly into
    > cisco1 with a crossover cable and get the same results 6) I do not get
    > these results when pinging cisco2's fastethernet interface with the same
    > command. It is at full duplex with 0 loss.
    >
    > This leads me to believe either:
    > 1) There is a problem with thing1's eth1 interface. It is a machine we
    > just connected recently, a clone of the older one, and we extensively
    > tested the ethernet ports for a week beforehand. 2) There is a problem
    > in cisco1's FastEthernet interface. 3) There is a reason that the
    > interface was manually set to half-duplex that I don't understand.
    > Neither of the other technicians, or the owner who installed the unit,
    > know why it was forced to half in the first place, though.
    >
    > I am not a master of Cisco equipment. Although I'm familiar with
    > networking and network troubleshooting, I've only really been
    > responsible for the Cisco IOS equipment in the last year and have been
    > reading books on how to use IOS.
    >
    > Does this sound like a problem in either of the units above, or is there
    > some specific reason that the interface should be set to half-duplex
    > that I'm missing or don't understand?
    >
    > ---------------------------
    > Michael Love,
    > SDC Technical Support
    > http://www.sdc.org



    "Both sides of a link should have auto-negotiation on, or both sides should have it
    off."

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


    If I misread, sorry,

    Rik Bain
    Rik Bain, Apr 9, 2004
    #2
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  3. Michael Love

    Michael Love Guest

    > "Both sides of a link should have auto-negotiation on, or both sides
    should have it
    > off."
    >
    >

    http://www.cisco.com/en/US/tech/tk389/tk214/technologies_tech_note09186a0080094781.shtml#when
    >
    >
    > If I misread, sorry,


    Thanks for the response, but I don't think this one applies to this
    situation:

    I have packet-loss problems when auto-negotiate is turned on both machines
    and they are plugged directly into each other, when they are set to
    auto-negotiate and they are connected to a switch, or when they are both
    manually set to full-duplex. The only time I don't have a problem is when
    the 2600 router is forced to half-duplex, and when it is set to full-duplex
    only the 2600 has problems.

    Another 2600 series router doesn't have problems at full-duplex. Tonight,
    I'm going to reconfigure to 2nd router and plug it into the exact port the
    older router is in and see if it works correctly or not.

    -------------------------------
    Michael Love,
    SDC Technical Support
    http://www.sdc.org
    Michael Love, Apr 9, 2004
    #3
  4. Michael Love

    AnyBody43 Guest

    "Michael Love" <> wrote in message news:<40767c83$>...
    > > "Both sides of a link should have auto-negotiation on, or both sides

    > should have it
    > > off."
    > >
    > >

    > http://www.cisco.com/en/US/tech/tk389/tk214/technologies_tech_note09186a0080094781.shtml#when
    > >
    > >
    > > If I misread, sorry,

    >
    > Thanks for the response, but I don't think this one applies to this
    > situation:
    >
    > I have packet-loss problems when auto-negotiate is turned on both machines
    > and they are plugged directly into each other, when they are set to
    > auto-negotiate and they are connected to a switch, or when they are both
    > manually set to full-duplex. The only time I don't have a problem is when
    > the 2600 router is forced to half-duplex, and when it is set to full-duplex
    > only the 2600 has problems.
    >
    > Another 2600 series router doesn't have problems at full-duplex. Tonight,
    > I'm going to reconfigure to 2nd router and plug it into the exact port the
    > older router is in and see if it works correctly or not.


    Hi,
    You could go old and grey worrying about this sort of thing.

    I confess that I have not read your description in detail
    'cos I am already sufficiently old and grey however
    while it is important to ensure that duplex settings match
    I have long given up worrying about whether auto works between
    this device and that device.

    So, just get it working cleanly and leave it at that.

    I now just try auto-auto and if that doesn't work out set
    BOTH ends, I always set speed and duplex if I am setting
    it manually. If one end is Auto Duplex and the other is not the
    auto end will (should?) always use HD.

    If there is a missmatch you will see Late Collisions on the HD side
    and Frame (Alignment) and/or CRC (FCS) on the FD end. Note that some
    traffic patterns could 'naturally' aviod collisions and so there
    may not be any errors at all even though there is a miss-match.

    Clearly it would be disappointing if Cisco kit did not interoperate
    but I personally would not go to mad about it in the case of
    a small installation. If I had a lot of ports to worry about then
    I would be bending TAC's ear a bit and getting it fixed.
    AnyBody43, Apr 11, 2004
    #4
  5. Michael Love

    Michael Love Guest

    My problem isn't worrying about the auto-negotiation. It's negotiating
    properly and setting itself correctly on both sides. What I'm having a
    problem with is packet-loss when it is set to full-duplex when no other
    device on the switch has a problem, including a 2nd 2600 router.

    I'm just asking if anyone else besides me thinks this is a problem with our
    router, or if there's something about 2600 configuration I don't understand.

    -------------------------------
    Michael Love,
    SDC Technical Support
    ,
    http://www.sdc.org

    "AnyBody43" <> wrote in message
    news:...
    > "Michael Love" <> wrote in message

    news:<40767c83$>...
    > > > "Both sides of a link should have auto-negotiation on, or both sides

    > > should have it
    > > > off."
    > > >
    > > >

    > >

    http://www.cisco.com/en/US/tech/tk389/tk214/technologies_tech_note09186a0080094781.shtml#when
    > > >
    > > >
    > > > If I misread, sorry,

    > >
    > > Thanks for the response, but I don't think this one applies to this
    > > situation:
    > >
    > > I have packet-loss problems when auto-negotiate is turned on both

    machines
    > > and they are plugged directly into each other, when they are set to
    > > auto-negotiate and they are connected to a switch, or when they are both
    > > manually set to full-duplex. The only time I don't have a problem is

    when
    > > the 2600 router is forced to half-duplex, and when it is set to

    full-duplex
    > > only the 2600 has problems.
    > >
    > > Another 2600 series router doesn't have problems at full-duplex.

    Tonight,
    > > I'm going to reconfigure to 2nd router and plug it into the exact port

    the
    > > older router is in and see if it works correctly or not.

    >
    > Hi,
    > You could go old and grey worrying about this sort of thing.
    >
    > I confess that I have not read your description in detail
    > 'cos I am already sufficiently old and grey however
    > while it is important to ensure that duplex settings match
    > I have long given up worrying about whether auto works between
    > this device and that device.
    >
    > So, just get it working cleanly and leave it at that.
    >
    > I now just try auto-auto and if that doesn't work out set
    > BOTH ends, I always set speed and duplex if I am setting
    > it manually. If one end is Auto Duplex and the other is not the
    > auto end will (should?) always use HD.
    >
    > If there is a missmatch you will see Late Collisions on the HD side
    > and Frame (Alignment) and/or CRC (FCS) on the FD end. Note that some
    > traffic patterns could 'naturally' aviod collisions and so there
    > may not be any errors at all even though there is a miss-match.
    >
    > Clearly it would be disappointing if Cisco kit did not interoperate
    > but I personally would not go to mad about it in the case of
    > a small installation. If I had a lot of ports to worry about then
    > I would be bending TAC's ear a bit and getting it fixed.
    Michael Love, Apr 12, 2004
    #5
  6. Michael Love

    AnyBody43 Guest

    "Michael Love" <> wrote in message news:<407a72b1$>...
    > My problem isn't worrying about the auto-negotiation. It's negotiating
    > properly and setting itself correctly on both sides. What I'm having a
    > problem with is packet-loss when it is set to full-duplex when no other
    > device on the switch has a problem, including a 2nd 2600 router.
    >


    I have now carefully read your material.

    "3) There is a reason that the interface was manually set to
    half-duplex that I don't understand. "?

    Sorry that this is a bit rude however in answer, how about:-

    Yes there may be, that's what made it work.
    What don't you understand?


    With one side HD fixed and the other Auto you should get HD-HD.

    Either something is lying about the attempted duplex setting (not
    unlikely) I understand or something is broken.

    In general I never trust duplex information from anything other
    than reputable network equipment and rely on inferring the duplex
    settings from the error counters of reputable network equipment.
    This is easy enough.

    As I have said:
    "If there is a missmatch you will see Late Collisions on the HD side
    and Frame (Alignment) and/or CRC (FCS) on the FD end. Note that some
    traffic patterns could 'naturally' aviod collisions and so there
    may not be any errors at all even though there is a miss-match."


    What I would recommend is to set it so that your testing
    indicates that the line is clean. In this instance you do not
    appear to need FD 100 anyway since you are connecting to the internet
    via a T1.

    If you want to pursue it then I will too.

    "Another 2600 series router doesn't have problems at
    full-duplex. Tonight, I'm going to reconfigure to 2nd
    router and plug it into the exact port the
    older router is in and see if it works correctly or not."

    Let me know if you want to pursue this further.
    AnyBody43, Apr 13, 2004
    #6
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