T1 Pt2PT Connection keeps dropping

Answered Question
Mar 16th, 2007
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We have a pt2pt connection configured and seems to keep dropping. The service provider changed out a bunch of equipment and seems to have help. I am new to the company and took a look at the configs and the t1 interfaces are both set to "line" on each end. Shouldnt one end be "internal"? It seems to have issues every 3 weeks or so. I was just wondering what has to happen for the timinig to be off and all of a sudden it keeps dropping if they are both set to line. Will this configuration work if both set to line and if something happens it drops becuase clocking is off.

Matt,


I am going to respectfully disagree with you. I used to support over a 100 T1 pt2pt connections and clocking was always provided on those lines. In addition I have done some work supporting a couple of small businesses with one or two remote sites, connected via T1, and clocking was always provided there as well. Maybe I am niave but it has always been my understanding that the clock was provided by telco on a T carrier. In fact in your situation I would think you would be seeing significant numbers of slip secs if you had two ends set for getting the clock from the line and in fact there were no clock.


Joe


Correct Answer by deigonza about 10 years 1 month ago

It could have been the repeater causing those drops on the line, hopefully your issue has been solved after the replacement made by the ISP.


Regarding the configuration register, 0x2102 is the correct one. If you need a link for future reference here is one with all the config register modes:


http://www.cisco.com/en/US/products/hw/routers/ps133/products_tech_note09186a008022493f.shtml



I hope this is useful,


Allan



PS, plz rate if helpful.

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jcorrale Fri, 03/16/2007 - 15:06
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Usually on p2p T1 circuits, Telco doesn?t provide clocking to the circuit, so we have to manually set ?clock source internal? on one of the routers. If you have line/line, then you can start seeing circuit drops or random disconnections like the ones you?re seeing now. Can you capture a ?show tech? of both ends?


Regards,


Juan


That is right, telco is definitely providing the clock. You can do a "show controller t1" and see if there are any slip secs or any other errors on the controller. I had a problem like this where the telco claimed nothing was wrong on their side, I replaced wic cards and eventually the routers on both sides. It turned out the whole time it as a bad smart-jack and telco replaced the card and I never saw the problem again.

matt.kurtzhals Mon, 03/19/2007 - 06:01
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I thought that the telco does not provide clocking on a point to point connection??? The line must have some kind of an error that excceds a certain threshold that causes the dropping because of the lack of clocking

deigonza Mon, 03/19/2007 - 06:37
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Hi Matt,


Few questions; for how long will the T1 stay down? what do you do to recover the service?


Are you getting slip seconds under the "show controllers t1" command output??

matt.kurtzhals Mon, 03/19/2007 - 06:46
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When I do a show controllers the serial interface says tx and rx clocks detected?? I also do not see the slip seconds. I did show controllers t1 and didnt get any output. So i did show controllers and found the serial interface.

deigonza Mon, 03/19/2007 - 07:06
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Ok, so it's not a VWIC card; what about the "show service-module interface SerialX/Y" command? What T1 card are you using, and IOS version?

deigonza Mon, 03/19/2007 - 07:07
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Ok, so it's not a VWIC card; what about the "show service-module interface SerialX/Y" command? What T1 card are you using, and IOS version?

matt.kurtzhals Mon, 03/19/2007 - 08:27
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Currently therre are no slip secs errors. After the telco replaced a repeater we have not had any issues for 4 days now. It would be good to know if the circuit does have issues in a week that it is the timing not set. Here is the output of sh inventory for the WIC


NAME: "WIC/VIC 2", DESCR: "WAN Interface Card - Serial (1T)"

PID: WIC-1T= , VID: 1.0, SN: 28878253


NAME: "WIC/VIC/HWIC 3", DESCR: "WAN Interface Card - DSU/CSU T1 Fractional (V2

PID: , VID: 1.2, SN: FOC101636CF


There is only one wic card not sure for the two entries. Here is the sh ver

(C2801-ADVSECURITYK9-M), Version 12.4(3c)


Also when I did a sh ver it said that the config register is 0x2102 is that correct? Seemed different for some reason.


Thanks,


Correct Answer
deigonza Mon, 03/19/2007 - 08:35
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It could have been the repeater causing those drops on the line, hopefully your issue has been solved after the replacement made by the ISP.


Regarding the configuration register, 0x2102 is the correct one. If you need a link for future reference here is one with all the config register modes:


http://www.cisco.com/en/US/products/hw/routers/ps133/products_tech_note09186a008022493f.shtml



I hope this is useful,


Allan



PS, plz rate if helpful.

matt.kurtzhals Mon, 03/19/2007 - 08:46
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Thanks for your help.. Should I be worried if both routers are set to "line" and the telco claims it does not provide the clocking?? Just watch for slip errors to determine if clocking is the issue.

matt.kurtzhals Mon, 03/19/2007 - 08:53
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Joe,


On Pt2Pt connections most of the time the telco does not provide the timing...

Correct Answer

Matt,


I am going to respectfully disagree with you. I used to support over a 100 T1 pt2pt connections and clocking was always provided on those lines. In addition I have done some work supporting a couple of small businesses with one or two remote sites, connected via T1, and clocking was always provided there as well. Maybe I am niave but it has always been my understanding that the clock was provided by telco on a T carrier. In fact in your situation I would think you would be seeing significant numbers of slip secs if you had two ends set for getting the clock from the line and in fact there were no clock.


Joe


matt.kurtzhals Mon, 03/19/2007 - 09:11
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I probably got some bad info then. Thanks Joe for your input. That is what our local telco claimed so I guess I believed them. I have not seen any slip errors so the timing must be coming from somewhere?????


Thanks,

Matt

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