Troubleshooting errors on 2950G interface, need help

Discussion in 'Cisco' started by Ole Vik, Nov 5, 2003.

  1. Ole Vik

    Ole Vik Guest

    Hi all.

    The scenario is this:

    We have a switch (Cisco 2950G) connected to a dsl modem on port 0/24.
    The port is configured as a trunk port, as we have a vlan segmented line.
    (Internal and secure zones).

    interface FastEthernet0/24
    description VLAN trunk
    switchport trunk allowed vlan 1,1002-1005,1179,1180
    switchport mode trunk
    no ip address
    speed 10
    duplex half


    (The modem is set to 10/half , so those settings are ok. )

    Communications over this line is extremely slow. Checking the interface for
    traffic shows that its not using even half of the bw.
    Ping times are usually good, but sometimes peaks at 200-300 ms for short
    periods of time.

    There is a lot of errors on this interface, and here is where i need help.

    Following is a sh controller output for this interface:

    02OSLSWI01#sh controllers ethernet-controller fastEthernet 0/24

    Transmit Receive
    232577791 Bytes 985654725 Bytes
    2341194 Frames 2304482 Frames
    120306 Multicast frames 44454 FCS errors
    10 Broadcast frames 0 Multicast frames
    0 Pause frames 8483 Broadcast frames
    15415 Single defer frames 0 Control frames
    0 Multiple defer frames 0 Pause frames
    948 1 collision frames 0 Unknown opcode frames
    354 2-15 collisions 44586 Alignment errors
    0 Late collisions 0 Length out of range
    0 Excessive collisions 0 Symbol error frames
    1687 Total collisions 0 False carrier errors
    0 Control frames 0 Valid frames, too small
    0 VLAN discard frames 0 Valid frames, too large
    0 Too old frames 27806 Invalid frames, too small
    2273476 Tagged frames 0 Invalid frames, too large
    0 Aborted Tx frames 0 Discarded frames


    FCS errors, alignment errors etc etc ... where do i begin?
    Checking cables are the obvious first step, but where do i go next?

    Best regards
    Ole Vik
    Ole Vik, Nov 5, 2003
    #1
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  2. In article <1068025632.826588@gurney>, Ole Vik <> wrote:
    :The scenario is this:

    :We have a switch (Cisco 2950G) connected to a dsl modem on port 0/24.
    :The port is configured as a trunk port, as we have a vlan segmented line.
    :(Internal and secure zones).

    :interface FastEthernet0/24
    : description VLAN trunk
    : switchport trunk allowed vlan 1,1002-1005,1179,1180
    : switchport mode trunk
    : no ip address
    :speed 10
    :duplex half
    :(The modem is set to 10/half , so those settings are ok. )


    Could I ask you to confirm for us that the dsl line itself is configured
    as an 802.1Q trunk? I do not recall ever having heard of an ISP
    providing such a thing before.

    DSL lines here are usually configured for PPP encapsulation (though
    I have heard of DSL with no encapsulation.)

    My first thought upon seeing your errors was "duplex mismatch".
    However, the sort of errors you are seeing could, I think, also be caused
    by trying to interpret a tagged line as untagged, or a PPP connection
    as not being encapsulated. I seem to recall that in theory
    trying to interpret an untagged line as tagged should be okay
    because I seem to recall that packets in the management vlan are not
    supposed to be tagged when sent across the VLAN... but if that's
    not accurate, then interpreting an untagged line as tagged could
    cause a mess too.
    --
    I was very young in those days, but I was also rather dim.
    -- Christopher Priest
    Walter Roberson, Nov 5, 2003
    #2
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  3. Ole Vik

    Ole Vik Guest

    Hi,

    The lines support IEEE 802.1Q , and is delivered with vlans in the range
    1000-3999.
    More info on www.catchspeed.no (Sadly only in Norwegian).

    The default Vlan 1 , is not in use, but i haven't bothered with removing it
    from any trunks.
    How much "mess" could this actually cause?

    Any more info on the Alignment, FCS and the Invalid Frame errors would be
    very much appreciated.


    Best Regards
    Ole Vik
    "Walter Roberson" <-cnrc.gc.ca> wrote in message
    news:boal8t$7uf$...
    > In article <1068025632.826588@gurney>, Ole Vik <>

    wrote:
    > :The scenario is this:
    >
    > :We have a switch (Cisco 2950G) connected to a dsl modem on port 0/24.
    > :The port is configured as a trunk port, as we have a vlan segmented line.
    > :(Internal and secure zones).
    >
    > :interface FastEthernet0/24
    > : description VLAN trunk
    > : switchport trunk allowed vlan 1,1002-1005,1179,1180
    > : switchport mode trunk
    > : no ip address
    > :speed 10
    > :duplex half
    > :(The modem is set to 10/half , so those settings are ok. )
    >
    >
    > Could I ask you to confirm for us that the dsl line itself is configured
    > as an 802.1Q trunk? I do not recall ever having heard of an ISP
    > providing such a thing before.
    >
    > DSL lines here are usually configured for PPP encapsulation (though
    > I have heard of DSL with no encapsulation.)
    >
    > My first thought upon seeing your errors was "duplex mismatch".
    > However, the sort of errors you are seeing could, I think, also be caused
    > by trying to interpret a tagged line as untagged, or a PPP connection
    > as not being encapsulated. I seem to recall that in theory
    > trying to interpret an untagged line as tagged should be okay
    > because I seem to recall that packets in the management vlan are not
    > supposed to be tagged when sent across the VLAN... but if that's
    > not accurate, then interpreting an untagged line as tagged could
    > cause a mess too.
    > --
    > I was very young in those days, but I was also rather dim.
    > -- Christopher Priest
    Ole Vik, Nov 5, 2003
    #3
  4. Ole Vik

    SKY Guest

    Alignment error: frames do not end with an even number of octets and had a
    bad CRC.

    FCS: frame check sequence error.

    All of these seems result from physical error. (cable, fa0/24 or dsl modem)

    besides check the cable, you could try changing another port to see if
    fa0/24 of the switch fault.
    And using another device on fa0/24 to see if the dsl modem fault

    regards,
    SKY


    "Ole Vik" <> ¦b¶l¥ó news:1068037622.19105@gurney ¤¤¼¶¼g
    ....
    > Hi,
    >
    > The lines support IEEE 802.1Q , and is delivered with vlans in the range
    > 1000-3999.
    > More info on www.catchspeed.no (Sadly only in Norwegian).
    >
    > The default Vlan 1 , is not in use, but i haven't bothered with removing

    it
    > from any trunks.
    > How much "mess" could this actually cause?
    >
    > Any more info on the Alignment, FCS and the Invalid Frame errors would be
    > very much appreciated.
    >
    >
    > Best Regards
    > Ole Vik
    > "Walter Roberson" <-cnrc.gc.ca> wrote in message
    > news:boal8t$7uf$...
    > > In article <1068025632.826588@gurney>, Ole Vik <>

    > wrote:
    > > :The scenario is this:
    > >
    > > :We have a switch (Cisco 2950G) connected to a dsl modem on port 0/24.
    > > :The port is configured as a trunk port, as we have a vlan segmented

    line.
    > > :(Internal and secure zones).
    > >
    > > :interface FastEthernet0/24
    > > : description VLAN trunk
    > > : switchport trunk allowed vlan 1,1002-1005,1179,1180
    > > : switchport mode trunk
    > > : no ip address
    > > :speed 10
    > > :duplex half
    > > :(The modem is set to 10/half , so those settings are ok. )
    > >
    > >
    > > Could I ask you to confirm for us that the dsl line itself is configured
    > > as an 802.1Q trunk? I do not recall ever having heard of an ISP
    > > providing such a thing before.
    > >
    > > DSL lines here are usually configured for PPP encapsulation (though
    > > I have heard of DSL with no encapsulation.)
    > >
    > > My first thought upon seeing your errors was "duplex mismatch".
    > > However, the sort of errors you are seeing could, I think, also be

    caused
    > > by trying to interpret a tagged line as untagged, or a PPP connection
    > > as not being encapsulated. I seem to recall that in theory
    > > trying to interpret an untagged line as tagged should be okay
    > > because I seem to recall that packets in the management vlan are not
    > > supposed to be tagged when sent across the VLAN... but if that's
    > > not accurate, then interpreting an untagged line as tagged could
    > > cause a mess too.
    > > --
    > > I was very young in those days, but I was also rather dim.
    > > -- Christopher Priest

    >
    >
    SKY, Nov 5, 2003
    #4
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