ADSL Keeps Dropping

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Dec 14th, 2009
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Hi Guys,


We have a ADSL connection which is connected back to our HQ via LANtoLAN VPN tunnel but the DSL connection keeps dropping. As far as I can tell there is nothing else connected to the line. I have pasted the output below of the show dsl int atm 0 command:


show dsl int atm 0
                ATU-R (DS)                      ATU-C (US)
Modem Status:    Showtime (DMTDSL_SHOWTIME)
DSL Mode:        ITU G.992.1 (G.DMT)
ITU STD NUM:     0x01                            0x01
Vendor ID:       'ALCB'                          'IFTN'
Vendor Specific: 0x0000                          0x711A
Vendor Country:  0x00                            0xB5
Capacity Used:   91%                             85%
Noise Margin:     6.5 dB                         10.0 dB
Output Power:    19.0 dBm                        12.0 dBm
Attenuation:     53.0 dB                         31.5 dB
Defect Status:   None                            None
Last Fail Code:  None
Selftest Result: 0x00
Subfunction:     0x15
Interrupts:      646 (1 spurious)
Activations:     1
Init FW:         embedded
Operartion FW:   embedded
SW Version:      3.9.220
FW Version:      0x1A04

                 Interleave             Fast    Interleave              Fast
Speed (kbps):          3072                0           512                 0
Reed-Solomon EC:      21051                0           187                 0
CRC Errors:              17                0            12                 0
Header Errors:           14                0             5                 0
Bit Errors:               0                0
BER Valid sec:            0                0
BER Invalid sec:          0                0

LOM Monitoring : Disabled

DMT Bits Per Bin
00: 0 0 0 0 0 0 0 4 6 7 8 8 8 9 8 8
10: 9 8 8 8 8 8 8 8 7 7 6 6 6 5 0 0
20: 0 0 0 0 0 0 7 7 8 8 8 9 9 9 A A
30: A A A A B A B B A A 7 8 A B B B
40: 0 B A A 8 7 8 7 4 0 0 0 A A A 9
50: A 8 A A A A 9 A A A A 2 A A A A
60: 9 A 9 9 7 9 9 8 8 8 7 5 3 2 0 0
70: 6 7 7 7 5 2 6 6 5 7 7 7 7 7 7 6
80: 6 6 6 5 4 0 2 0 0 2 3 4 4 4 4 4
90: 4 4 4 0 6 6 4 6 0 5 6 6 5 5 5 4
A0: 5 5 5 4 4 2 0 0 0 2 2 3 4 4 3 0
B0: 2 2 2 2 0 0 0 0 0 0 0 0 0 0 0 0
C0: 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
D0: 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
E0: 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
F0: 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0

Training log buffer capability is not enabled yet.



Can someone please tell me if this looks normal or if there is something wrong with the router. Oh and its a Cisco 837 IOS version 12.3 (4) T7.


Thanks,

Ross.

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Giuseppe Larosa Tue, 12/15/2009 - 00:14
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Hello Ross,

line parameters are not bad.

Noise Margin:     6.5 dB                         10.0 dB


you may want to try with a newer DSL firmware a way to load  a newer one is to load a new IOS image.


I would try with a 12.4(T) version.



Hope to help

Giuseppe

Ganesh Hariharan Tue, 12/15/2009 - 00:30
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Hi,


Spurious interrupts found on the device. A spurious interrupt occurs when
an unnecessary interrupt is raised for an already processed packet, possibly due
to an internal race condition or improper initialization of interrupt handling
routines. They can be ignored, if in small numbers as there is no discernable impact
on the behavior of the router due to spurious interrupts. Spurious interrupts can
be caused either by defective hardware or by software. If the performance is degrading
with increasing number of spurious interrupts then check for any known bugs at
Bug Toolkit.


The Attenuation value is high. Attenuation is a decrease in the strength
of a signal over the length of a cable. The optimum value is in the range of 20db
to 50db. A value of more than 50db can depress the bit rate.
TRY THIS: If the modems train at a low bit rate or the line experiences too many
errors then repair or replace the cables and connectors in the loop.


Hope this helps to some extent !!


Regards

Ganesh.H

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