Siegbert Marschall wrote:
Hi,
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Physical connection: #
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We are terminating with this carrier in a FE port but due to the
distance between them and us at the datacenter location, a FDDI
connection was placed in between like:
[our
router]----[100baseTX]----[IMC**]----//..fiber..//----[IMC**]----[100baseTX]----[switch
integrated in a Cisco 7200 iron]----[Cisco iron itself/router]
* Attenuation on the FDDI part was 1.2db respectively 1.3db which is not
brilliant, but okay. More importantly it's within the specifications of
the IMC's.
** (IMC = MOXA Industrial Media Converter 101 a.k.a. IMC-101 for both
Single- and Multi mode / SC connectors. We even replaced these with MOXA
EDS-208-M-SC (larger model) as well).
I think here you have the Problems. I can't see any FDDI stuff in this
drawing so I will assume for the moment that is just a "FDDI" type fiber
you are connected to and everything else is Ethernet. The IMC-101 is
just a plain media-converter without any Layer-2 capabilities according
to http://www.moxa.com/product/IMC-101.htm but they are not completely
dumb devices, so one has to be careful with them.
I chose Moxa because we have very good experiences with their other
products (embedded solutions, RS-232 etc.) and because the IMC-101 (and
EDS-208) all comply with the IEEE802.3 standard - and from the Moxa
doc.:"..provides industrial grade media conversion between
10/100BaseT(X) and 100BaseFX."
Maybe I've presumed too much, but I took (from the above) layer-2
capabilities as granted.
In the connection above there is something very important to know:
Autonegotiation activated in any part of the setup is a bit like playing
russian roulette. Either the whole chain supports it perfectly or you are
f****d. Make sure that you have Autonegotiation off _everywhere_ and
everything is set and bolted to Fullduplex otherwise you might get the
strangest and hard to trace errors. I helped someone troubleshoot a
similar setup at his decix connection a few years ago and they've been
swapping media-converters back and forth till we just used a switch
as media converter catching the FDX/HDX issue in the middle so the
end's where happy and some people where wondering for a few weeks
to who the new mac address (of the switch) belonged which suddenly
appeared in the decix mesh till the link got switched over to fiber
end to end.
I'm well aware of that particular problem which is why I gave the new
carrier a list of "termination settings" firsthand and later we've also
went up and down all the speed- and duplex-mode (and other) setting
during the troubleshoot (another nice feature that initially added to
the "go-list" on the Moxa IMC's was indeed the dip switch on Moxa's
converters giving an opportunity to choose between 'auto' and
'full-duplex').
I think you are on to something / you are right about the (maybe)
missing layer-2 feature and/or a faulty FDX/HDX issue.
About the mac; I can almost picture the wrinkles in someones forehead :)
I am not of the opinion of the other poster, media-converters are
not bad. But the are devices which need to be treated with respect,
not everything can be transparently converted to other media.
there normally aren't any flp-pulses on fiber since it is FDX by
nature, so FDX/HDX negotiation is troublesome. some converters
emulate it or catch the autoneg but wether the equipment you connect
to the converter is capable of actually talking to it is also not
for sure.
-sm
Thank you very much for your thorough answer Siegbert and it's been nice
to hear from someone who has been through the same exercise.
/per
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