ADSL2 MODEM ISSUE ON ATM INTERFACE

[veltech]

Hi All,

We have a strange problem on an 1801 with ADSL2 modem built in.

We have configured the ATM interface for a Plus Net ADSL2+ service which is basically the same as BT. We get sync and showtime OK but then the ATM interface starts going up and down about every 20 seconds or so. Here is the "sh dsl interface" output.

ATM0

Alcatel 20190 chipset information

                ATU-R (DS)                      ATU-C (US)

Modem Status:    Showtime (DMTDSL_SHOWTIME)

DSL Mode:        ITU G.992.1 (G.DMT) Annex A

ITU STD NUM:     0x03                            0x3

Vendor ID:       'STMI'                          'TSTC'

Vendor Specific: 0x0000                          0x0510

Vendor Country:  0x0F                            0xB5

Chip ID:         C196 (0)

DFE BOM:         DFE3.0 Annex A (1)

Capacity Used:   98%                             70%

Noise Margin:     6.5 dB                         14.0 dB

Output Power:    18.0 dBm                        12.5 dBm

Attenuation:     53.0 dB                         31.5 dB

Defect Status:   None                                           LCDi

Last Fail Code:  None

Watchdog Counter: 0x2D

Watchdog Resets: 0

Selftest Result: 0x00

Subfunction:     0x00

Interrupts:      751703 (0 spurious)

PHY Access Err:  0

Activations:     163

LED Status:      ON

LED On Time:     100

LED Off Time:    100

Init FW:         init_AMR-3.0.014_no_bist.bin

Operation FW:    AMR-3.0.014.bin

FW Source:       embedded

FW Version:      3.0.14

                 Interleave             Fast    Interleave              Fast

Speed (kbps):          2208                0           448                 0

Cells:                    5                0         12953                 0

Reed-Solomon EC:        700                0             8                10

CRC Errors:             476                0            11                 9

Header Errors:          461                0             6                 7

Total BER:                5641E-6                0E-0

Leakage Average BER:      5641E-6                0E-0

                        ATU-R (DS)      ATU-C (US)

Bitswap:               enabled            enabled

Bitswap success:          0                   0

Bitswap failure:          0                   0

LOM Monitoring : Disabled

Has anyone any idea what could be causing this to cycle up and down?

Thanks.

[Leo Laohoo · Accepted solution]

You've got one bad copper line.

Attenuation and Noise values are off the chart.

ADSL: Significance of SNR and attenuation

[veltech]

Hi,

Thanks for the quick response. Yes, the SN and attenuation are border line but the connection works fine with a Draytek modem (Vigor 120). We also had BT out today as we had issues with sync on the line, but that turned out to be a poor connection in the cabnet. Anymore ideas about how we can get a fix for this issue?

Thanks.

[Leo Laohoo]

Post the "sh interface atm" output.

I am waiting for Paolo to chime in here. 

[James Neilson · Accepted solution]

First thing I would do is upgrade the DSL firmware to version 0.0.026 this was specifically designed for the UK DSLAMS on ADSL2+. You should see an immediate improvement in the noise margin.

http://software.cisco.com/download/release.html?mdfid=279624018&softwareid=282821763&release=6.0.010&relind=AVAILABLE&rellifecycle=&reltype=latest

While the above link is for an 877 the FW works with the 1801, just make sure to use the 0.0.026 verison not the 6.0.010 verison

[veltech]

Hi All,

Thank you all for your comments and help.

We have now sorted out this problem with BT directly and it was the SN ratio, which was around 6db which the Cisco just won't accept. The BT engineer and I spent some time earlier today tweaking the SN ratios and we now have what seems to be a stable connection on the Cisco box. Interestingly we hooked up a Draytek Vigor 120 and that seemed pretty happy at a much lower SN of 5 or 6. It also seems that the customer site is on the distance limit from the exchange. So I think it is fair to say that this problem was the SN ratio as suggested initially by Leo, so I have given him the correct answer.

Thank again to all of you.

regards,

[veltech]

Also meant to say that James provided the correct firmware for BT which I felt was also a correct answer.

Regards,

[Leo Laohoo]

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