can you loop a frac t1 card with the interface admin down?

Unanswered Question
Dec 12th, 2007

Hi, I have an interface that i can't turn up due to it being in production.... the site tech says that he saw the lights normalize on the circuit when a loop was put on the circuit. that was news to me. the second time the loop came up he didn't see it at the router-- is it possible to loop a card with the interface admin shut?

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swmorris Wed, 12/12/2007 - 06:46

In short, it depends on how things are setup. You have two separate pieces, the router and the CSU/DSU. Your router interface may be administratively down, but you'll still get things functioning at the controller side (Layer 1).

So in short, yes, if you are remotely looping the built-in DSU you may see the CD light go green even though the interface on the router is administratively shutdown.



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lgontarsk Wed, 12/12/2007 - 06:52

Thanks for your response, Scott.

I didn't quite get the "maybe" part... if the circuit is good and the loop is seen by the card, will the cd led go green even while the interface is shut down?

Lisa G

swmorris Wed, 12/12/2007 - 06:55

Two different "interfaces" on the router.

Controller interface is the smart-jack. if you have this shutdown, then no, your lights won't work (and you won't be able to remotely loop it).

Serial interface is what the router will use for setting up the L2 link/L3 routing. If this is shutdown, you won't try to route anything, but you can still get your green lights and looping.



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lgontarsk Wed, 12/12/2007 - 07:30

Hi Scott,

Thanks for the clarification.

This is a service module.... looks to me like it is up and not shut down, and that we should have seen the cd light go green when the loop was put up on the circuit. do you agree?


ruralcellular2-alexandria-mn#show service-module s 0/2/0

Module type is T1/fractional

Hardware revision is 0.48, Software revision is 20060322,

Image checksum is 0x3EFB7B, Protocol revision is 0.1

Transmitter is sending AIS.

Receiver has Remote alarm,

Framing is ESF, Line Code is B8ZS, Current clock source is line,

Fraction has 24 timeslots (64 Kbits/sec each), Net bandwidth is 1536 Kbits/sec.

Last module self-test (done at startup): Passed

Last clearing of alarm counters 3w1d

loss of signal : 3, last occurred 23:35:26

loss of frame : 4, last occurred 00:59:55

AIS alarm : 0,

Remote alarm : 5, current duration 00:37:30

Module access errors : 0,

Total Data (last 96 15 minute intervals):

68207 Line Code Violations, 22 Path Code Violations

0 Slip Secs, 2567 Fr Loss Secs, 37 Line Err Secs, 2 Degraded Mins

2 Errored Secs, 0 Bursty Err Secs, 2147483647 Severely Err Secs, 2572 Unavail Secs

Data in current interval (534 seconds elapsed):

0 Line Code Violations, 0 Path Code Violations

0 Slip Secs, 0 Fr Loss Secs, 0 Line Err Secs, 0 Degraded Mins

0 Errored Secs, 0 Bursty Err Secs, 0 Severely Err Secs, 0 Unavail Secs


swmorris Wed, 12/12/2007 - 07:34

You are receiving remote alarm currently it appears.

As for the CD light, that would depend on which type of loop code they threw at you. There are different types of loops, some of which will create the illusion of CD, some of which will not.

So I can't fully answer that question, but it is possible, yes.


Richard Burts Wed, 12/12/2007 - 06:51


I have not tried it so I can not say for sure. But I would be very surprised if you could loop the card if the interface was admin down - if we are talking looping from the router to the smart jack. If they are looping the circuit at the smart jack or looping at the router toward the smart jack then the loop should work.




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