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Simple stupid fiber question on Cisco 7301 and 3550 switch

 
 
Rea Michaels
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      07-19-2004

A customer I spoke with has a Cisco 7301 router with
GigabitEthernet0/1 plugged in to a 3550 switch. The customer claims
the GigabitEthernet0/1 on the Cisco 7301 showed down, but the 3550
switch showed the circuit up. I'm a fiber newbie, so my simple stupid
question is; Can one side of a fiber ciruit show up, and the other
side show down?"

Thanks,

Rea

 
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Walter Roberson
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      07-19-2004
In article <40fc220a.2211770@127.0.0.1>,
Rea Michaels <(E-Mail Removed)> wrote:
: A customer I spoke with has a Cisco 7301 router with
:GigabitEthernet0/1 plugged in to a 3550 switch. The customer claims
:the GigabitEthernet0/1 on the Cisco 7301 showed down, but the 3550
:switch showed the circuit up. I'm a fiber newbie, so my simple stupid
:question is; Can one side of a fiber ciruit show up, and the other
:side show down?"

It happens. I've never seen an explanation for it, but I have seen
people posting here saying it has happened to them.


Some possibilities pulled out of thin air:

- sensitivities of the receivers differ, the link is borderline,
the connectors need to be cleaned

- gigabit is spec'd to automatically figure out details like crossovers
and duplex, but there have been reports that it doesn't always work on
all manufacturers

- difference between "line protocol is up" and "line is administratively
up"
--
How does Usenet function without a fixed point?
 
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fearo
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      07-21-2004
On Mon, 19 Jul 2004 19:34:15 +0000, Rea Michaels wrote:

>
> A customer I spoke with has a Cisco 7301 router with
> GigabitEthernet0/1 plugged in to a 3550 switch. The customer claims the
> GigabitEthernet0/1 on the Cisco 7301 showed down, but the 3550 switch
> showed the circuit up. I'm a fiber newbie, so my simple stupid question
> is; Can one side of a fiber ciruit show up, and the other side show down?"
>
> Thanks,
>
> Rea


There are two things that come to mind in this situation that I have seen
myself.

1) port negotiation. Best results are achieved with this disabled on both
ends.

2) flow control. Best results if both ends are set to "desired" for send
and recieve packets.


 
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