T1 Problems?

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Jul 11th, 2007
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I'm having some trouble w/ a T1 line that I've been troubleshooting. The link is steady (doesn't lose connectivity), but as soon as we start to pass traffic through it the data rate drops exponentially. Its like we're on an old 56k line when transferring files.


We have a cisco router w/ a serial WIC card which connects to an adtran. Then we connect through copper lines (w/ a pair gain on each end) to another building that houses the service provider equipment.


Not sure how to continue troubleshooting this, could the slow datarates be due to the pairgains / copper lines? Or could it be a configuration on the routers?


Any help is always appreciated.


Thanks!

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paolo bevilacqua Wed, 07/11/2007 - 05:42
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Show interface please ?


jkloza Wed, 07/11/2007 - 06:25
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Serial0/0 is up, line protocol is up

Hardware is PowerQUICC Serial

Interface is unnumbered. Using address of FastEthernet0/0

MTU 1500 bytes, BW 1544 Kbit, DLY 20000 usec, reliability 255/255, txload 2/255, rxload 1/255 Encapsulation PPP, LCP Open

Open: IPCP, loopback not set

Keepalive set (10 sec)

Last input 00:00:01, output 00:00:01, output hang never

Last clearing of "show interface" counters

Input queue: 0/75/741/0 (size/max/drops/flushes); Total output drops: 8178

Queueing strategy: fifo

Output queue: 0/40 (size/max)

5 minute input rate 4000 bits/sec, 4 packets/sec

5 minute output rate 15000 bits/sec, 3 packets/sec

100172440 packets input, 379597156 bytes, 3 no buffer

Received 0 broadcasts, 1 runts, 7 giants, 0 throttles

542073 input errors, 17165 CRC, 295988 frame, 0 overrun, 0 ignored, 228913 abort

97376318 packets output, 2994254947 bytes, 0 underruns

0 output errors, 0 collisions, 3788 interface resets

0 output buffer failures, 0 output buffers swapped out

252 carrier transitions

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



Serial0/0 is up, line protocol is up

Hardware is PowerQUICC Serial

Interface is unnumbered. Using address of FastEthernet0/0

MTU 1500 bytes, BW 1544 Kbit, DLY 20000 usec, reliability 255/255, txload 1/255, rxload 6/255

Encapsulation PPP, LCP Open

Open: IPCP, 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 20:38:14

Input queue: 0/75/212/0 (size/max/drops/flushes); Total output drops: 2581

Queueing strategy: fifo

Output queue: 0/40 (size/max)

5 minute input rate 42000 bits/sec, 11 packets/sec

5 minute output rate 12000 bits/sec, 11 packets/sec

4140450 packets input, 919647042 bytes, 0 no buffer

Received 0 broadcasts, 1 runts, 1 giants, 0 throttles

165683 input errors, 7814 CRC, 76389 frame, 0 overrun, 0 ignored, 81477 abort

4307778 packets output, 2715868322 bytes, 0 underruns

0 output errors, 0 collisions, 61 interface resets

0 output buffer failures, 0 output buffers swapped out

31 carrier transitions

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



pciaccio Wed, 07/11/2007 - 06:57
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You are getting excessive input errors and output drops. Try clearing the counters on both sides and see what the results show then. If the errors continue then you may have a T-1 issue. Do you know what has been provisioned to you by your carrier? Is it a full T-1. Also how are the end point CSU's setup for? Can you do a SHOW CONTROLLER T-1 from both sides to see the layer 1 stats of the line.....

jkloza Wed, 07/11/2007 - 09:47
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Yes, its a full T1, not a fractional.. There are no T1 controllers on the router, it shows none. The router just handles the physical connection, the adtran actually has the line coding, and framing on it..


Its an old setup, but I'm confident that it shouldn't be as slow as it is now.



vinay_verma80 Sun, 07/15/2007 - 15:44
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hi


u have huge no of errors , that means ur line is faulty


165683 input errors, 7814 CRC, 76389 frame, 0 overrun, 0 ignored, 81477 abort <<<<<< contact ur servive provider if the same status after clearing the conter


" u can read my note on this form in Lease line problem"


252 carrier transitions << ur interface in go down and again coming up check the modem, clabele b/w router and the modem


regards

scottmac Wed, 07/11/2007 - 06:43
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Check your LAN (not WAN) setting to verify that the DUPLEX (FUll / Half) are properly set and match at both ends.


Also check your cabling; if any of it is hand-made (versus "store-bought"), try replacing it with known good.


The problem is much more likely to be a LAN problem at one end or the other than a T1 problem, given the problem you've described.


Please post a "SH INT" for (at least) the serial interface(s) you're using to the WAN and the Ethernet LAN interfaces.


Good Luck


Scott

jkloza Wed, 07/11/2007 - 06:53
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I did think that this may be a problem. On the LAN side there's a hub which the f0/0 plugs into which is a half duplex hub (not my design, just what was in place lol :P).


The S0/0 interfaces use ip unnumbered and take the ip address of the FA0/0 interface (again not my design)... The fa0/0 interface is running at 100/half because its connected to the hub.. Could this be a factor in the datarates? I can probably replace with a 10/100 switch to get at least full duplex connectivity..

jkloza Wed, 07/11/2007 - 06:54
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I did think that this may be a problem. On the LAN side there's a hub which the f0/0 plugs into which is a half duplex hub (not my design, just what was in place lol :P).


The S0/0 interfaces use ip unnumbered and take the ip address of the FA0/0 interface (again not my design)... The fa0/0 interface is running at 100/half because its connected to the hub.. Could this be a factor in the datarates? I can probably replace with a 10/100 switch to get at least full duplex connectivity..

paolo bevilacqua Wed, 07/11/2007 - 07:46
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Hi,


Your T1 circuit using pairgain is working poorly. Likely a clock problem. Please check with the ISP that one of the pairgain units is generating clock.

Do not close the ticket until the error counter stays zero or very small over a 48h time period.



jkloza Wed, 07/11/2007 - 09:48
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Ok, so the pairgains actually generate clocking, or they are in theory supposed to? I wasn't aware, I know the provider is generating the clocking, just I don't know where.

paolo bevilacqua Wed, 07/11/2007 - 10:47
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It is a "dry pair" circuit, so one pairgain unit has to generate clock on the loop, and the other will receive clock.

Both units are always giving clock toward the DTE (router), problem is that currently either something is very wrong with the physical loop, or as I said the units are not configured correctly.


You can pretty much exclude any router responsibility in a case like yours.


Good luck!

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