how to check this ?

A t1 is provided to a customer.. If the customer's router is turned off or if the T1 cable is bad or removed from the smart jack to the router , I see that "serial is down and line protocol as down". I checked cisco website and they give these

1. Check the LEDs on the CSU/DSU to see whether the CD is active, or insert a breakout box on the line to check for the CD signal.

2. Verify that you are using the proper cable and interface (see your hardware installation documentation).

3. Insert a breakout box and check all control leads.

4. Contact your leased-line or other carrier service to see whether there is a problem.

5. Swap faulty parts.

6. If you suspect faulty router hardware, change the serial line to another port. If the connection comes up, the previously connected interface has a problem.

My end is a 7206 router and it shows " serial is down and line protocol is down".. The telecom company says that they can loop until the smart jack but could not loop to the CSU/DSU.. They obviously cannot if the router is dead or shutdown or the cable from smart jack to router is bad or disconnected..

Is there a way I can loop until the Smartjack from my  7206 for this interface and determine that the problem is the cable or router ??  The whole purpose for me is that If I know the problem is in the router or cable from smartjack , I donot have to open a troubleticket with the telecom company and that can save time.


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You could put a T-1 hardware loopback plug into your router interface to see if you get line up proto up. This would tell it is or is not the router.

Check it out:

sunray_2003Author Commented:

Here is a slight problem.. I donot have access to either of the routers. I can telnet to the 7206 and thats how i see
serial is down and line protocol is down.

If the serial is up and line protocol is down , I see I can do loopback tests and if the interface comes up then it could be telecom issue.. I am looking for a similar tests if both serial and line protocol are down..
is the csu/dsu internal or external to the router?
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sunray_2003Author Commented:

At the customer end there is a 1720 router and CSU/DSU is internal to the router..
sunray_2003Author Commented:
Here is the config on my 7206 for this customer

controller T3 1/1
 framing m23
 clock source line
 t1 1 channel-group 0 timeslots 1-24

interface Serial1/1/1:0
 ip address
 encapsulation ppp

If I do "sh int serial 1/1/1:0" and I get this

Serial1/1/1:0 is down, line protocol is down
  Hardware is PA-MC-2T3+
  Internet address is
  MTU 1500 bytes, BW 1536 Kbit, DLY 20000 usec,
     reliability 254/255, txload 1/255, rxload 1/255
  Encapsulation PPP, LCP Closed, crc 16, loopback not set
  Keepalive set (10 sec)
  Last input 09:50:15, output 09:50:13, output hang never
  Last clearing of "show interface" counters 4d04h
  Input queue: 0/75/0/0 (size/max/drops/flushes); Total output drops: 181
  Queueing strategy: weighted fair
  Output queue: 0/1000/64/181 (size/max total/threshold/drops)
     Conversations  0/7/16 (active/max active/max total)
     Reserved Conversations 0/0 (allocated/max allocated)
     Available Bandwidth 1152 kilobits/sec
  5 minute input rate 0 bits/sec, 0 packets/sec
  5 minute output rate 0 bits/sec, 0 packets/sec
     2009808 packets input, 382470320 bytes, 0 no buffer
     Received 0 broadcasts, 0 runts, 0 giants, 0 throttles
     2 input errors, 1 CRC, 0 frame, 0 overrun, 0 ignored, 1 abort
     2155782 packets output, 728318307 bytes, 0 underruns
     0 output errors, 0 collisions, 0 interface resets
     0 output buffer failures, 0 output buffers swapped out
     0 carrier transitions alarm present
  Timeslot(s) Used: 1-24, subrate: 1536Kb/s, transmit delay is 0 flags
  non-inverted data


What are the steps, I can do to loop until the smart jack at the customer location ?
sunray_2003Author Commented:
Any suggestions ?
sorry...missed the previous comment.

It sounds like you don't have any visibility on the remote router at all...So, youneed to have the carrier loop the smartjack back towards your 7200 and you should see your circuit come up/up(looped). If that is indeed what happens, and having the carrier release the loop, it goes down/down, I'd start with the cable on the remote side (the 1700) or perhaps interface/csu/dsu configuration.

sunray_2003Author Commented:

So your point is if my "shw interface serial " on my  7206 shows , serial is down and Line protocol is down , I cannot do anything on my end other than asking the carrier to do loopback of the smartjack.. If that is what it is going to be , then fine. I can just call the carrier and request them to do the loopback of the smartjack..  

The overall purpose of this question is that "If I can do any prior testing and If yes , what can be done "..
I see I can do the prior software loopback if serial is UP and Line protocol is down. Just wondering if I can do a similar testing if both are down.
Well, anytime you're troubleshooting a circuit, I always work from the bottom of the stack.

If they bring it up and you're still down/down, and they say they can 'see' the smartjack, have them loop it back towards your router...that way, it eliminates the possibility that they haven't horked up the circuit buildout on their side first. Because carriers never screw up circuit builds <wink>....

So, unless you've got modem or some other access into the remote router, there's not really much you can do without the carrier's help. If they loop the smartjack back to you and you dont' see anything, I'd say the carrier has some work to do, since it appears that the t1 is being provisioned off of your channelized ds3, so I doubt the problem is on your side.

If you see the loop, then you'll have to have them drop the loop and contact whoever is your 'remote hands' on the customer prem.

sunray_2003Author Commented:
I donot seem to find the option of looping a serial interface in 7206.
Is it just

router<config>#interface serial 1/1/1:0
router<config-if># loopback   <==== I donot seem to have this loopback option..
you don't really need to loop anything, unless the carrier loop at the remote smartjack doesn't come up, but like I said, if your ds3 is up already, it's not likely that you'll need to do any circuit loops from the 7200 site of the circuit.

How you loop an interface depends upon your equipment. Looks like with the channelized ds3, you're not going to do it from the interface command, but rather the controller construct:

Here's an example of the config section you should be looking for:
controller T3 1/1
 framing m23
 cablelength 224
 mdl string port 1/1
 mdl string generator 1
 t1 1 channel-group 0 timeslots 1-24
 t1 2 channel-group 0 timeslots 1-24
 t1 3 channel-group 0 timeslots 1-24
 t1 4 channel-group 0 timeslots 1-24
 t1 5 channel-group 0 timeslots 1-24
 t1 6 channel-group 0 timeslots 1-24
 t1 7 channel-group 0 timeslots 1-24
 t1 8 channel-group 0 timeslots 1-24
 t1 9 channel-group 0 timeslots 1-24
 t1 10 channel-group 0 timeslots 1-24
 t1 11 channel-group 0 timeslots 1-24
 t1 12 channel-group 0 timeslots 1-24
 t1 13 channel-group 0 timeslots 1-24
 t1 14 channel-group 0 timeslots 1-24
 t1 15 channel-group 0 timeslots 1-24
 t1 16 channel-group 0 timeslots 1-24
 t1 17 channel-group 0 timeslots 1-24
 t1 18 channel-group 0 timeslots 1-24
 t1 19 channel-group 0 timeslots 1-24
 t1 20 channel-group 0 timeslots 1-24
 t1 21 channel-group 0 timeslots 1-24
 t1 22 channel-group 0 timeslots 1-24
 t1 23 channel-group 0 timeslots 1-24
 t1 24 channel-group 0 timeslots 1-24
 t1 25 channel-group 0 timeslots 1-24
 t1 26 channel-group 0 timeslots 1-24
 t1 27 channel-group 0 timeslots 1-24
 t1 28 channel-group 0 timeslots 1-24

and how you go about looping any of the specific channels:
sunray_2003Author Commented:
If serial is UP and line protocol is down and the telecom carrier says that they can loop until the smartjack fine , then Is this the way to loop until the CSU/DSU (the CSU/DSU is inbuilt in the router)

router#config t
router(config)# controller t3 1/1
router(config-controller)# t1 1 loopback remote

and then check sh interface serial 1/1/1:0 to see if the line protocol comes up .. Is this the correct procedure ?
up/down indicates a problem on layer2...i.e. it's generally an LMI-type mismatch/configuration issue.

And again, that would probably be on the remote side rather than the channellized ds3 side, unless it's down for the whole ds3.

Make sense?

If they can get to the remote smartjack, they should be able to throw up a loop towards your 7200/ds3 and it should show up/up(looped). When they remove it and it shows up/down, you'll need to look at the remote router's LMI-type in the config.

sunray_2003Author Commented:
Kind of make sense but what I would like to do is to  put the serial interface in a loopback and do a show interface.
atleast that would be the starting learning experience..

The telecom and our carrier are doing testing still.. might get some result by tonite or tommorrow

what is that LMI-type that I should be looking at the remote adtran 612 router
You'll have to ask the carrier what they are using. It doesn't really matter what you use, as long as you and the carrier are using the same thing :)

sunray_2003Author Commented:

It was afterall a bad CFA at the carrier's CO.. They changed it and the T1 came up fine.. Just wanted to update you.
Thanks for all your help/suggestions


Usually you have to exhaust any possibility of problems on your end before the carrier even contemplates investigating their side.

Glad it's all working.

sunray_2003Author Commented:

Would you mind taking a look at this..
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