[c-nsp] loop-testing 10G with cisco?

Gert Doering gert at greenie.muc.de
Thu Dec 11 07:27:25 EST 2008


I'm facing a new challenge and hope that one of you has a nice trick for

We are working on taking a 10G wavelength into service, and it has packet
errors (CRC errors showing up on one side).  3 different fiber providers
involved, plus local in-house cabling.  Difficult.

For "classic" lines (T1 to STM-<whatever> serials), the normal approach to
diagnosing this is to loop back the fiber at certain points of the path,
and see which part is the problematic one.

This works with 10G fiber as well, but I can't find a way to ping-test 
the loop from the Cisco.

Here's the setup:

Cisco 6506, Sup720-10GE  =======<fiber path>======) loop cable

I can *see* the loop ("show cdp neighbor" shows myself, and if UDLD is
enabled, the interface goes to errdisable).  

I just can't ping-test, as the router is clever(?) enough to locally 
loop the packets - self-ping won't leave the box.  On a serial interface, 
pinging myself will make the router send out the packet over the serial, 
so I can nicely ping-test the loop.

So - what's the trick for testing such things with a 10GE LAN interface?

USENET is *not* the non-clickable part of WWW!
Gert Doering - Munich, Germany                             gert at greenie.muc.de
fax: +49-89-35655025                        gert at net.informatik.tu-muenchen.de
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