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Problems with T1 clock source

deberly900
Beginner
Beginner

We have a point to point T1 from Verizon using a clock source on the one side (uses the standard command: service-module t1 clock source internal). Both routers are 1601R's and they are both running version 12.0(8). We have had these routers in place for almost four years without incident. Recently, the T1 has begun dropping on an intermittant basis. Verizon has tested several times without finding any errors. They believe it is our clock source. Unfortunately, I don't have a lot of experience with router configs and am at a loss as to how to proceed. Any assistance will be greatly appreciated.

Thanks!

PS.: Please advise as to any additional info needed.

13 Replies 13

amit-singh
Collaborator
Collaborator

Hi,

Ganerally, we use the clock source provided by telco on the line. I would suggest you to change the clock source to line instead of internal. command : Got to config mode

controller T1 6/0

framing ESF

channel-group 0 timeslots 1-31

service-module t1 clock source line

Please check the following link and it will come handy.

http://www.cisco.com/en/US/tech/tk713/tk628/technologies_tech_note09186a00800a758d.shtml#perfhardplug

HTH,

-amit singh

Amit,

Thanks so much for the info. Unfortunately, I now have more info than I did when I originally wrote the message. My boss was dealing with the Verizon engineer. Evidently, he told us that there may or may not be clocking on the line. Does that sound reasonable and if so, where do we go from here?

Thanks again...

yes it does, Telco might decide not to sync it to their network..if telco uses "loop" timing at all DS1 interfaces .

Otherwise, they set each transmitter to master and use their clock distribution system as the external source to sync the transmit to the telco network.thus providing you clocking .

can you post your "show interface serial x output"

Olufemi,

Thank you! Here is my serial output from both ends of the T1.

CENTRAL LOCATION

Serial1 is up, line protocol is up

Hardware is HD64570

Internet address is 10.21.0.1/16

MTU 1500 bytes, BW 1544 Kbit, DLY 20000 usec, rely 255/255, load 3/255

Encapsulation HDLC, loopback not set, keepalive set (10 sec)

Last input 00:00:05, output 00:00:00, output hang never

Last clearing of "show interface" counters never

Input queue: 0/75/0 (size/max/drops); Total output drops: 145

Queueing strategy: weighted fair

Output queue: 0/64/138 (size/threshold/drops)

Conversations 0/22 (active/max active)

Reserved Conversations 0/0 (allocated/max allocated)

5 minute input rate 19000 bits/sec, 14 packets/sec

5 minute output rate 24000 bits/sec, 14 packets/sec

16408916 packets input, 2548491689 bytes, 0 no buffer

Received 177232 broadcasts, 0 runts, 0 giants

23340 input errors, 23340 CRC, 1100 frame, 0 overrun, 0 ignored, 381 abort

16521609 packets output, 3759067403 bytes, 0 underruns

0 output errors, 0 collisions, 1 interface resets

0 output buffer failures, 0 output buffers swapped out

2 carrier transitions

DCD=up DSR=up DTR=up RTS=up CTS=up

REMOTE LOCATION

Serial1 is up, line protocol is up

Hardware is QUICC Serial (with FT1 CSU/DSU WIC)

Internet address is 10.121.0.2/16

MTU 1500 bytes, BW 1544 Kbit, DLY 20000 usec, rely 255/255, load 1/255

Encapsulation HDLC, loopback not set, keepalive set (10 sec)

Last input 00:00:00, output 00:00:00, output hang never

Last clearing of "show interface" counters never

Input queue: 0/75/0 (size/max/drops); Total output drops: 660

Queueing strategy: weighted fair

Output queue: 0/1000/64/0 (size/max total/threshold/drops)

Conversations 0/26/256 (active/max active/max total)

Reserved Conversations 0/0 (allocated/max allocated)

5 minute input rate 25000 bits/sec, 5 packets/sec

5 minute output rate 3000 bits/sec, 4 packets/sec

177280328 packets input, 2918610694 bytes, 19 no buffer

Received 2816433 broadcasts, 0 runts, 15 giants, 19 throttles

51034689 input errors, 28392547 CRC, 13632440 frame, 0 overrun, 0 ignored,

9009697 abort

169434143 packets output, 964429514 bytes, 0 underruns

0 output errors, 0 collisions, 1989 interface resets

0 output buffer failures, 0 output buffers swapped out

533 carrier transitions

DCD=up DSR=up DTR=up RTS=up CTS=up

it is really hard to point at a problem now. since the counters have never been cleared for both interfaces.

can you clear the counters to ensure you are getting current information.

99% of the time you are going to set both sides of your network to line timing which is the default. Do that first. Then if you are still getting input errors put a local loop at the telco at one side and then clear the counters, then look to see if you are getting input errors at such after five minutes. If you are then you know the problem is between your router and the telco. If you don't get errors then move the loop to the Distant end pointing back to you, clear the counters and see if get any errors. Continue this until you find out where you are getting problems.

No problem. I cleared them yesterday morning around 9:00 am Eastern Time. Here they are:

CENTRAL LOCATION

fp-hv#show int s1

Serial1 is up, line protocol is up

Hardware is QUICC Serial (with FT1 CSU/DSU WIC)

Internet address is 10.121.0.1/16

MTU 1500 bytes, BW 1544 Kbit, DLY 20000 usec, rely 255/255, load 1/255

Encapsulation HDLC, loopback not set, keepalive set (10 sec)

Last input 00:00:00, output 00:00:00, output hang never

Last clearing of "show interface" counters 22:56:33

Input queue: 0/75/0 (size/max/drops); Total output drops: 3

Queueing strategy: weighted fair

Output queue: 0/1000/64/0 (size/max total/threshold/drops)

Conversations 0/25/256 (active/max active/max total)

Reserved Conversations 0/0 (allocated/max allocated)

5 minute input rate 2000 bits/sec, 2 packets/sec

5 minute output rate 1000 bits/sec, 2 packets/sec

634500 packets input, 184433794 bytes, 0 no buffer

Received 12155 broadcasts, 0 runts, 0 giants, 0 throttles

3738 input errors, 1946 CRC, 1543 frame, 0 overrun, 0 ignored, 249 abort

652038 packets output, 299404218 bytes, 0 underruns

0 output errors, 0 collisions, 105 interface resets

0 output buffer failures, 0 output buffers swapped out

20 carrier transitions

DCD=up DSR=up DTR=up RTS=up CTS=up

REMOTE LOCATION

FANDANGO#show int s1

Serial1 is up, line protocol is up

Hardware is QUICC Serial (with FT1 CSU/DSU WIC)

Internet address is 10.121.0.2/16

MTU 1500 bytes, BW 1544 Kbit, DLY 20000 usec, rely 255/255, load 1/255

Encapsulation HDLC, loopback not set, keepalive set (10 sec)

Last input 00:00:00, output 00:00:00, output hang never

Last clearing of "show interface" counters 22:58:57

Input queue: 1/75/0 (size/max/drops); Total output drops: 2

Queueing strategy: weighted fair

Output queue: 0/1000/64/0 (size/max total/threshold/drops)

Conversations 0/26/256 (active/max active/max total)

Reserved Conversations 0/0 (allocated/max allocated)

5 minute input rate 1000 bits/sec, 3 packets/sec

5 minute output rate 0 bits/sec, 0 packets/sec

651835 packets input, 299089431 bytes, 0 no buffer

Received 12164 broadcasts, 0 runts, 0 giants, 0 throttles

1276902 input errors, 721196 CRC, 336932 frame, 0 overrun, 0 ignored, 21877

4 abort

634758 packets output, 184459782 bytes, 0 underruns

0 output errors, 0 collisions, 105 interface resets

0 output buffer failures, 0 output buffers swapped out

20 carrier transitions

DCD=up DSR=up DTR=up RTS=up CTS=up

FANDANGO#

You have had 105 interface resets which is not good. Have you done the local loops yet to determine if you have a local problem?

No, unfortunately, I'm not well versed with your instructions. I know enough to create simple configs and run various commands. I have contacted Verizon, and they instructed me to contact them as soon as the circuit goes down again and they will check the stats on the cards.

I'm not sure what else to do at this point. We don't have anyone at the remote site to assist us.

Okay, Verizon has done all the local loop testing requested above. CSU to CSU tested clean. Where do I go from here? Thanks!

I had a similar problem with my point to point T1, I changed the clock source to every configuration, I pulled a new cable form the smart jack and all along the telco is telling me it's my problem. They tested it numerous times and it was always clean. After a month of continous calls to them they sent a local tech out to test the line, before he tested it he told me that my area's cables were in bad shape and he knew where the problem was. They rerouted my circuit thru another area and I havent had any problems since. My advice is: Stay On Them, they will always say it isnt there problem. If it turns out that it wasnt there problem then you can always say your sorry.

Thanks so much for the info. I was actually starting to think the same thing. I can't see why my routers would just start "acting up." I'll keep trying with Verizon to see what I can get them to do.

Actually what I meant by local loop is to have the CSU go into local loop mode and look at the router. The data stream will be sent out the router to the CSU/DSU through the loop and right back at the same router. If you do a show interface on the router, it will usually see that it is looped and up and up, from there clear the counters and see if you see any errors come in, if you do then you know you have a problem between the router and the CSU/DSU. If you don't look at the other router, it should see itself in a far end loop (if not, throw its DSU/CSU in a loop and test again) and you should be able to determine from those tests where you are getting errors at.

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