[TriLUG] Slightly OT: network switch question

Tue May 15 20:17:34 EDT 2018

Thanks guys. Good thoughts. I’ll run this by the IT group that owns the switch.

Sent from my iPad

> On May 15, 2018, at 8:15 PM, Aaron Joyner <aaron at joyner.ws> wrote:
> 
> I agree with David, that sounds like an auto link negotiation problem.  When the physical link disconnects and reconnects, the primary thing that happens is the Ethernet connection is renegotiated.  This establishes if it's 10/100/1000, half or full duplex, mdi/mdix, etc.  If there is a problem negotiating, and they disagree, the connection may be down until they renegotiate.  Unplugging and reconnecting the cable forces that renegotiation.
> 
>> On Tue, May 15, 2018, 7:25 PM David Brain via TriLUG <trilug at trilug.org> wrote:
>> Port speed (re)negotiation problems?  That would explain the
>> disconnect/reconnect fix.
>> 
>> 
>> On Tue, May 15, 2018, 5:37 PM Matt Flyer via TriLUG <trilug at trilug.org>
>> wrote:
>> 
>> > Mike,
>> >
>> > Thank you for the reply.  Good information.
>> >
>> > In this case it is a static IP address so it isn't a lease question.
>> >
>> > Some more information that may be pertinent.  Ping to the remote end of
>> > the bridge shows "Host network unreachable" (I think it was) and ARP is
>> > showing 'incomplete'.  It is all on the same LAN segment but there are
>> > switches and what not in between.
>> >
>> > The lights on the switch were hard to see but it looks like the
>> > connection light (green) was light and the yellow activity light was
>> > blinking, but slower than expected.  It is almost as if the device or
>> > port had gone to a non configured state or something.
>> >
>> >
>> > On Tue, 2018-05-15 at 17:22 -0400, Mike Lisanke wrote:
>> > > Just a thought, but if one or both routers are connected as Dynamic
>> > > IP to upstream... then on may have missed its lease renewal and
>> > > removing+restoring the Ethernet cable would have been detected and
>> > > new lease request issued resolving a problem... for Static IP
>> > > assignment, that wouldn't apply. I've had cascaded routers loose
>> > > their Dynamic but assigned IP and reboot/reconnect resolves the
>> > > problem... I never looked closer as to why the lease was allowed to
>> > > expire without proper renewal.
>> > >
>> > > On Tue, May 15, 2018 at 3:00 PM, Matt Flyer via TriLUG <trilug at trilug
>> > > .org> wrote:
>> > > > I have an application that uses two wireless modems, running Linux
>> > > > as
>> > > > their OS, as a wireless Ethernet bridge.  The devices have been up
>> > > > for
>> > > > a little over 5 years without issue until about six months ago when
>> > > > the
>> > > > link stopped working.  At the time, removing and reinserting the
>> > > > network cable between the main building network switch and one of
>> > > > the
>> > > > modems got things working again.
>> > > >
>> > > > Last Saturday they stopped communicating again.  I did a reset of
>> > > > both
>> > > > of the wireless modems.  In one case, I pulled the POE / Ethernet
>> > > > cable
>> > > > out of the modem performing a power reset on it.  Similarly on the
>> > > > other modem, I performed a power reset by pulling the AC plug on
>> > > > the
>> > > > POE injector as the modem is physically inaccessible without a lift
>> > > > /
>> > > > bucket truck.  This had no effect and did not solve the problem.
>> > > >
>> > > > I was reviewing some documentation on the previous failure and
>> > > > noticed
>> > > > that it got 'fixed' when someone pulled the Ethernet cable between
>> > > > the
>> > > > building switch and the POE injector.  This would have interrupted
>> > > > the
>> > > > communications, but not power reset the wireless modem.  It would
>> > > > have
>> > > > also broken the physical connection as far as the building switch
>> > > > was
>> > > > concerned.
>> > > >
>> > > > My question is, what happens at the switch when you pull the
>> > > > network
>> > > > cable and break the circuit?  More importantly, what happens that
>> > > > could
>> > > > have caused things to 'reset'? I am starting to think that this is
>> > > > a
>> > > > switch problem and not an issue with the wireless modem, which is
>> > > > what
>> > > > I had initially assumed.
>> > > >
>> > > > My knowledge of Ethernet doesn't go down to the physical level, so
>> > > > I
>> > > > thought I would throw this question out in the hopes that someone
>> > > > has
>> > > > an idea.
>> > > >
>> > > >
>> > > >
>> > > > --
>> > > > This message was sent to: Mike Lisanke <mike.lisanke+trilug at gmail.c
>> > > > om>
>> > > > To unsubscribe, send a blank message to trilug-leave at trilug.org
>> > > > from that address.
>> > > > TriLUG mailing list : https://www.trilug.org/mailman/listinfo/trilu
>> > > > g
>> > > > Unsubscribe or edit options on the web  : https://www.trilug.org/ma
>> > > > ilman/options/trilug/mike.lisanke%2Btrilug%40gmail.com
>> > > > Welcome to TriLUG: https://trilug.org/welcome
>> > >
>> > >
>> > --
>> > This message was sent to: dbrain at gmail.com <dbrain at gmail.com>
>> > To unsubscribe, send a blank message to trilug-leave at trilug.org from that
>> > address.
>> > TriLUG mailing list : https://www.trilug.org/mailman/listinfo/trilug
>> > Unsubscribe or edit options on the web  :
>> > https://www.trilug.org/mailman/options/trilug/dbrain%40gmail.com
>> > Welcome to TriLUG: https://trilug.org/welcome
>> -- 
>> This message was sent to: Aaron S. Joyner <aaron at joyner.ws>
>> To unsubscribe, send a blank message to trilug-leave at trilug.org from that address.
>> TriLUG mailing list : https://www.trilug.org/mailman/listinfo/trilug
>> Unsubscribe or edit options on the web  : https://www.trilug.org/mailman/options/trilug/aaron%40joyner.ws
>> Welcome to TriLUG: https://trilug.org/welcome