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New Member

Clocking Issue on point to point T1

I am getting a high number of errors on a point to point t1. The t1 provider has told me that the circuit is fine and it appears to be a clocking issue on my end since they do not provide any clocking on a point to point. One end is a 3640 router with a WIC-1DSU-T1 and the other end is a 1721 router. The current config is very basic (encap ppp, ip address, no ip-directed broadcast). After doing some research I tried to configure one end with the "service-module t1 clock source internal" command but the interface will not come up (serial1/1 down, line protocol down). Any suggestions for correcting the clocking problem would be appreciated.

6 REPLIES
Bronze

Re: Clocking Issue on point to point T1

Setting one to internal and one to line (the default) should do it. Is this what you have now? If so, maybe try reversing the clocking settings and see if that changes anything.

Cisco Employee

Re: Clocking Issue on point to point T1

Telco will always say service/line is fine.. Now what errors you are seeing it?

Clocking should always come from line. If its a point to point t1, and telco can't provide a clock on it, then clock source should be internal on 3600. But what about the clock source on 1721? is it internal or from line?

If serial interface is down/down, thatmay not be the only issue with clocking. There may be other issues too.

New Member

Re: Clocking Issue on point to point T1

By default the 1721 clock source is set to line - but when I set the 3640 to clock source internal the interface will never come up. I have 2 point to point T1s coming into the 3640 router with identical configs. S1/0 shows almost no errors and S1/1 is the interface with the problems. Last week the T1 provider took the circuit down and tested and said the errors were probably clocking problems on our end. I cleared the counters of each interface 3 days ago and below shows the results of "show service-modules S1/x"

SH SERVICE-MODULE S1/1

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 2d15h): Passed

Last clearing of alarm counters 2d15h

loss of signal : 0,

loss of frame : 9, last occurred 01:57:30

AIS alarm : 0,

Remote alarm : 1, last occurred 2d15h

Module access errors : 0,

Total Data (last 96 15 minute intervals):

0 Line Code Violations, 0 Path Code Violations

2262 Slip Secs, 8097 Fr Loss Secs, 0 Line Err Secs, 0 Degraded Mins

16265 Errored Secs, 0 Bursty Err Secs, 8097 Severely Err Secs, 0 Unavail Ses

Data in current interval (524 seconds elapsed):

0 Line Code Violations, 0 Path Code Violations

10 Slip Secs, 49 Fr Loss Secs, 0 Line Err Secs, 0 Degraded Mins

88 Errored Secs, 0 Bursty Err Secs, 49 Severely Err Secs, 0 Unavail Secs

SH SERVICE-MODULE S1/0

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 2d15h

loss of signal : 0,

loss of frame : 0,

AIS alarm : 0,

Remote alarm : 1, last occurred 2d15h

Module access errors : 0,

Total Data (last 96 15 minute intervals):

0 Line Code Violations, 0 Path Code Violations

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

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

Data in current interval (396 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

New Member

Re: Clocking Issue on point to point T1

I had the same problem with 2 2610's. After speaking and troubleshooting the routers with cisco engineers the main problems where always the telco lines. The tel. company denied it and sent a tech to verify the line. After the technician worked on it the line came up with the telco providing the clocking. So a suggestion is to verify the serial circuit.

Hope it helps.

Jorge

New Member

Re: Clocking Issue on point to point T1

If you have two t-1's coming into the 3640, could you not swing them over to each others interface and see if the problem follows the line or stays on the same interface?

New Member

Re: Clocking Issue on point to point T1

I have switched both T1s on the 3640 to the other wic-1dsu-t1 and the problems stayed with the same circuit. I also started a case with Cisco who had me do a loopback test on both ends which indicated no problems. I got the impression from the tech that if the router at both ends of the circuit are set to clock source line than the circuit had to be providing clocking otherwise the circuit would not come up. Is this correct? I cannot get the circuit to come up if I set one end to clock source internal. Since the loopback test was successful the tech said it had to be a framing or clocking problem with the telco. The telco claims they do not provide any clocking.

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