[c-nsp] switch port "shutdown" and "no shutdown"- what exactly happens?

[Peter Pauly]

You can also try something like this:

http://parts.digikey.com/1/parts/672213-ferrite-cylinder-clamp-black-28a0640-0a2.html

and put it on your ethernet cable.  Even better would be to loop it
through a couple times instead of just once.



On Thu, Jun 2, 2011 at 9:49 AM, Andrew Koch <andrew.koch at gawul.net> wrote:
> On Thu, Jun 2, 2011 at 06:07, Martin T <m4rtntns at gmail.com> wrote:
>> Hi,
>> rather stupid subject, but the thing is, that I have one Cisco
>> WS-C2950-24 switch, which has one Motorola radio device connected to
>> one of fast-ethernet ports:
>>
>> WS-C2950-24[Fa0/1] <-> [eth]Motorola_radio_device
>>
>> Problem is, that about once every 24h this connection stops forwarding
>> traffic. I have changed the fast-ethernet ports in WS-C2950-24 switch
>> and even replaced the switch with a new one, I have replaced the
>> Motorola_radio_device, there are no interface flaps and errors on
>> switch port, nothing interesting in the Motorola_radio_device log
>> file. Both devices are behind the proper UPS. Once the traffic between
>> those two devices stops, simple "shutdown" and "no shutdown" to the
>> switch port helps. Cat5e cable between the devices is 75m(246 feet)
>> long. One might suspect the cable/connectors, but on the other hand
>> there really are no errors on the switch port. What might cause the
>> issue where reinitialization of the Ethernet port reallows traffic
>> forwarding? Might there be a possibility to reproduce such situation
>> in the lab?
>
> Hi Martin,
>
> You mention this Motorola device is a radio.  Is this a receiver only,
> or a transmitter also?  Is it putting out a signal of considerable
> strength?  I have seen all sorts of odd troubles when RFI gets induced
> into a device that is not intended of receiving it, including
> completely seizing up.  Assuming this is a transceiver, I wonder if
> you have proper grounding of the radio so that it puts its RF to
> ground rather than to that nice cable you strung for your ethernet
> connectivity.  Also, have you isolated the radio from the switch -
> used fiber or an isolator block?
>
> This only happens on the 24th?  Is the radio setup to do something on
> that day, such as a pre-scheduled test?
>
> Being that the cable is 75m, it may also be acting as an antenna.
> Again, changing this to a fiber connection would eliminate this
> potential pickup of noise.  Using a properly terminated shielded cable
> may also be a choice.  If neither of these are feasible, you could run
> the ethernet cabling through a ferrite core at each end that would
> prevent some noise from entering the switch and radio.
>
> As far as the specifics in the switch during a shut/no shut, I am not
> certain.  However, if the radio is inducing bits to flip in registers
> or overloading the ethernet port receiver, resetting the port may
> refire the receiver correctly.
>
> HTH,
> Andy Koch
> KC9GXN
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