Cisco 877(W) on a BT A-DSL line

Hello,

dependant on your ios and/or router :

dsl operating-mode ?

adsl2 adsl2 mode adsl2+ adsl2+ mode ansi-dmt ANSI full rate mode

In addition to Luc's comments I have seen this happen on 877 with IOS

12(1) - I think the Cisco website says you need 12(3) onwards to support ADSL2 etc...is your IOS the latest? J

I don't need ADSL2+ yet. My line is only ADSL1. I'm just wondering whether the ADSL2+ support in the hard- and software cause my stability problems.

It's pretty new:

Cisco IOS Software, C870 Software (C870-ADVIPSERVICESK9-M), Version 12.4(9)T1, RELEASE SOFTWARE (fc2)

Kind regards

yes, I have seen this symptom on low-quality PSTN line. Please send to us the result of 'sh dsl interface atm0' ........

Best regards,

Considering the fact that it's 15m to the exchange and that my previous router (Netgear DG834G), my current modem (Linksys ADSL2MUE) and the Cisco 877W all connect at the maximum speed that BT's Max DSL can provide I don't think my line qualifies as a low-quality PSTN line.

Because I'm not using the Cisco at the moment I'm not sure whether the output is accurate:

jumpgate#show dsl int atm0 ATM0 Alcatel 20190 chipset information Line not activated: displaying cached data from last activation ATU-R (DS) ATU-C (US) Modem Status: Showtime (DMTDSL_STOP) DSL Mode: ITU G.992.1 (G.DMT) Annex A ITU STD NUM: 0x03 0x1 Vendor ID: 'STMI' 'ALCB' Vendor Specific: 0x0000 0x0000 Vendor Country: 0x0F 0x0F Capacity Used: 82% 99% Noise Margin: 1.0 dB 5.0 dB Output Power: 16.5 dBm 12.0 dBm Attenuation: 10.0 dB 4.0 dB Defect Status: LCDf LOS LOF LCDf Last Fail Code: None Watchdog Counter: 0x7D Watchdog Resets: 0

Selftest Result: 0x00 Subfunction: 0x00 Interrupts: 15357 (0 spurious) PHY Access Err: 0 Activations: 8 LED Status: OFF LED On Time: 100 LED Off Time: 100 Init FW: embedded Operation FW: embedded FW Version: 2.5.42

Interleave Fast Interleave Fast Speed (kbps): 0 8128 0 832 Cells: 0 118 0 64884 Reed-Solomon EC: 0 0 174 187 CRC Errors: 0 1797 286 1096 Header Errors: 0 1428 291 743 Total BER: 0E-0 0E-0 Leakage Avarage BER: 0E-0 2E-0

Kind regards

The downstream noise margin @ 1.0 dB is very low and likely causing the disconnects. Ideally it should be around 6.0 dB at a minimum.

The DSLAM hardware at the exchange should learn to stabilise your line over a period of 10 days (if I remember correctly) by automatically reducing the downstream syncronisation rate (you're currently running at the maximum line speed of 8128 kbps), which in turn will increase your downstream noise margin (SNR ~ Signal-to-Noise Ratio).

If for some reason the DSLAM fails to negotiate a stable speed over time I believe you can contact your ISP and request a higher noise margin be manually specified (say, 10 dB) to force stability at the expense of maximum line rates.

I see. 6.0 dB is what the old Netgear DG834G reported.

I do *not* think it is is related to the line:

- I have BT-Max since April this year. I never had any problems to operate the line at 8Mb/Sec with the Netgear DG834G or the Linksys ADSL2MUE. I only bought the Cisco because I wanted a router with IPv6 support to get rid of the seperate Unix box acting as firewall.

- After the Cisco 877W failed to provide stable A-DSL service yesterday I switch back to the Linksys ADSL2MUE. It connected at 8Mb/Sec immediately and hasn't lost the connection since. I've even run "ping" at a 5 second interval against my ISP's "ping server" overnight. It didn't lose a single packet.

So whatever causes the problem is related to the Cisco. My best guess that it is somehow not working well with both microfilters I tried.

I must say that I'm somewhat disappointed that a "high-end DSL router" obviously struggles to provide the same quality of service as a ten times cheaper DSL modem.

Kind regards

If you have support raise a TAC case.

I have seen several issues with 877 and ADSL. Cisco are in fact publishing ADSL firmware updates independently of IOS.

FW Version: 2.5.42 The latest is something like 3.0.10 and 2.6.4 is available. This has been discussed in an earlier thread.

I think that 12.4(9)T2 may be available too.

There is clear evidence of line issues, noise margin as mentioned already and actual line errors.

Interleave Fast Interleave Fast Speed (kbps): 0 8128 0 832 Cells: 0 118 0

64884 Reed-Solomon EC: 0 0 174 187 CRC Errors: 0 1797 286 1096 Header Errors: 0 1428 291 743 Total BER: 0E-0 0E-0 Leakage Avarage BER: 0E-0 2E-0

Reed-Solomon EC are a count of successful Error Correction events. I guess CRC and Header errors indicate cases that Error Correction has failed.

I have had success by manually configuring the dsl operating mode.

Your unit seems to be using:- DSL Mode: ITU G.992.1 (G.DMT) Annex A

So set it to:- dsl operating mode itu.dmt

I would try them all until I found one that worked.

I suspect that BT usually support several different ones.

Many parameters (incliding speed) are set at the Provider end only as I understand it.

Interestingly the Downstream direction is reporting errors in both Interleave and Fast mode suggesting negotiation difficulties.

I agree that it is odd that Cisco seem to be having trouble providing ADSL kit that works as well as consumer level kit seems to.

Comments similar to yours are something that I have come across quite a bit recently (only with 857/877 I think) not with 837 but they are almost obsolete now (certainly for 8M I would guess).

Finally you can turn on the DSL training log. It produces a lot of output none of which makes much sense to me but you never know there might be a clue in there. I have read that enabling logging increases the time to train up.

I deal with say 20 sites.

877 is otherwise rather nice and I have not yet failed to get one going (IIRC).

You can get the latest ADSL firmware for 800 series direct from Cisco's FTP site: (you do not currently need CCO access)

ftp://ftp.cisco.com PUblic, Access, 800 , DSL firmware.

There are instructions there, but bacically rename the file to ADSL_ALC_20190.bin and copy it to the routers Flash & reboot.

cheers,

Peter.

snipped-for-privacy@hotmail.co.uk wrote:

[...]

That was a great hint. Thanks a lot! I've update the firmware for the ADSL modem from 2.5.42 to 3.0.1 and things look much better now:

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 [...] Capacity Used: 79% 97% Noise Margin: 11.0 dB 6.0 dB Output Power: 14.5 dBm 12.0 dBm Attenuation: 7.0 dB 4.0 dB [...] Interleave Fast Interleave Fast Speed (kbps): 0 8128 0 768 Cells: 0 509117 0 1468564 Reed-Solomon EC: 0 0 0 0 CRC Errors: 0 8 0 0 Header Errors: 0 0 0 0 Total BER: 0E-0 1176E-11 Leakage Avarage BER: 0E-0 1176E-11

I had lots and lots of errors previously while I onlt got 8 in several minutes now. And there's noise on the phone line either. And network performance looks good, too:

ttcp-t: 1835008 bytes in 2.19 real seconds = 819.66 KB/sec +++

Kind regards