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High Attenuation on Cisco 877

My ADSL line frequently drops out of sync when using the ADSL 877 - the line attenuation is 43dB when the cisco is plugged in, and 23dB when it is not. I don't experience any drop out problems with other gateways.

Suggestions?

15 REPLIES
Hall of Fame Super Gold

Re: High Attenuation on Cisco 877

You can try upgrading ADSL FW to 3.0.33, that can be accessed at:

ftp://ftp.cisco.com/pub/access/800

There is a docfile about installation.

Please rate post if it helps!

New Member

Re: High Attenuation on Cisco 877

Thanks, that improved it quite a bit, down to 33dB, but that's still 10x what it is without the gateway connected up. It's 26dB with a Billion 7300G connected up to it (and 23dB without).

Hall of Fame Super Gold

Re: High Attenuation on Cisco 877

What is the actual connection speed and how far away are you from CO ?

New Member

Re: High Attenuation on Cisco 877

About 9000/1000Mbps, 150m away from the exchange.

Hall of Fame Super Gold

Re: High Attenuation on Cisco 877

You mean 9M down and 1M upload, matches what you have contracted ? Does the line still drops ?

New Member

Re: High Attenuation on Cisco 877

As in it syncs at 9M down and 1M up. Haven't experienced any drops since upgrading the firmware though the drops usually occur every 1-2 days (only been a few hours).

Hall of Fame Super Gold

Re: High Attenuation on Cisco 877

Ok, my question was about the speed that you have contracted with ISP, is that 9/1 ?

New Member

Re: High Attenuation on Cisco 877

Oh, 24/2.5.

Hall of Fame Super Gold

Re: High Attenuation on Cisco 877

Hi,

beside that faster than 1.3Mbps upload requires an annex M model router, and your probably is not, I'm not sure what else you can do. Assuming the internal wiring is proper (filters, spiices, etc).

New Member

Re: High Attenuation on Cisco 877

The speed isn't the problem, it's that the line keeps dropping out of sync.

I know it's a problem with the Cisco gateway, when I connect it up, the noise on the line goes up 10-100x (it should have a negligible effect).

What I want to know is if it's a problem with my specific gateway, or the series in general.

Hall of Fame Super Gold

Re: High Attenuation on Cisco 877

Is the line dropping again with the current FW ? I guess you have to wait few days before being able to state if it does.

What do you mean with "when I connect it up, the noise on the line goes up 10-100x" ?

New Member

Re: High Attenuation on Cisco 877

Just dropped today again.

When it's physically connected to the line, the line attenuation goes up from 23dB to 33dB-43dB.

Hall of Fame Super Gold

Re: High Attenuation on Cisco 877

How do you measure the attenuation when router is not connected to the line?

If you are comparing with figures taken using another router model, you cannot really do that, due to the differences in HW and vendor implementation.

However, in either cases, your values are far too high to confirm the fact you're 150m from the dslam. Also indicating a possible problem with cabling, the fact that attenueation as reported by the 877, varies from 33 to 43 dB. That should not happen.

When reporting problem, the entire "show dsl interface" should be posted. This is because there are other important values, like SNR and capacity used.

You can try adding some resilience to transient noise configuring "snr margin current" and "snr margin snext". Try a value of 5 dB.

New Member

Re: High Attenuation on Cisco 877

The attenuation measurements are down by my ISP both with the gateway connected and without:

wNet#show dsl int atm0

ATM0

Alcatel 20190 chipset information

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

Modem Status: Showtime (DMTDSL_SHOWTIME)

DSL Mode: ITU G.992.5 (ADSL2+) Annex A

ITU STD NUM: 0x03 0x2

Chip Vendor ID: 'STMI' 'BDCM'

Chip Vendor Specific: 0x0000 0x619F

Chip Vendor Country: 0x0F 0xB5

Modem Vendor ID: 'CSCO' ' '

Modem Vendor Specific: 0x0000 0x0000

Modem Vendor Country: 0xB5 0x00

Serial Number Near: FHK1207263E

Serial Number Far:

Modem Version Near: 12.4(4)T8

Modem Version Far:

Capacity Used: 99% 99%

Noise Margin: 11.5 dB 11.5 dB

Output Power: 19.5 dBm 12.0 dBm

Attenuation: 33.0 dB 18.0 dB

Defect Status: None None

Last Fail Code: None

Watchdog Counter: 0x1F

Watchdog Resets: 0

Selftest Result: 0x00

Subfunction: 0x00

Interrupts: 8263 (0 spurious)

PHY Access Err: 0

Activations: 3

LED Status: ON

LED On Time: 100

LED Off Time: 100

Init FW: init_3.0.33_nobist.bin

Operation FW: AMR-3.0.033.bin

FW Version: 3.033

DS Channel1 DS Channel0 US Channel1 US Channel0

Speed (kbps): 0 9311 0 1048

Cells: 0 8269 0 270643

Reed-Solomon EC: 0 0 0 0

CRC Errors: 0 117 0 0

Header Errors: 0 112 0 0

Interleave Delay: 0 0 0 0

LOM Monitoring : Disabled

DMT Bits Per Bin

000: 0 0 0 0 0 0 0 8 9 A B B C C C C

010: C C C C C D C C C C C B B B A 9

020: 0 4 0 0 0 9 0 B A A A B A A A A

030: A A B B B B B B B B B B B B B B

040: C B B B B B B B B B B B B B B B

050: B B B 2 B B B B B A B B B B B B

060: B B B B B A B A A A A A A A A A

070: A A A A A A A A A A A A A A A 9

080: A 9 A A A 9 A 9 9 9 9 9 9 A 9 9

090: 9 9 9 9 9 9 9 9 9 9 9 9 9 9 9 9

0A0: 9 9 9 9 9 9 9 9 9 9 9 9 9 9 9 9

0B0: 8 9 9 8 9 9 9 8 9 8 8 8 8 8 9 8

0C0: 8 8 8 7 2 6 7 8 8 8 8 8 8 8 8 8

0D0: 8 8 8 8 8 8 8 8 8 8 8 8 8 8 8 8

0E0: 8 8 8 8 8 8 8 8 8 8 8 8 8 8 8 8

0F0: 8 8 7 7 4 7 7 7 7 8 7 7 7 7 7 7

100: 7 7 7 7 6 2 7 7 7 7 7 7 4 7 7 7

110: 7 7 6 6 6 6 4 0 0 4 5 5 6 6 6 6

120: 6 6 6 6 6 6 5 6 6 5 6 6 5 6 5 5

130: 5 5 5 5 5 5 5 5 5 5 5 5 5 4 4 4

140: 4 4 4 4 4 4 4 4 4 4 4 4 4 4 0 4

150: 4 4 3 4 3 3 3 2 2 2 2 2 2 2 2 2

160: 2 2 2 2 2 1 2 2 2 2 2 2 2 2 2 2

170: 2 2 2 1 1 1 1 0 0 0 0 0 0 0 1 0

180: 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0

190: 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0

1A0: 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0

1B0: 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0

1C0: 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0

1D0: 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0

1E0: 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0

1F0: 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0

DSL: Training log buffer capability is not enabled

I noticed that Noise Margin changes to -8.5dB when it loses sync.

Hall of Fame Super Gold

Re: High Attenuation on Cisco 877

The thing is that this doesn't seem to be a very good line:

- SNR is a acceptable, but a bit on the low side.

- Frequencies seems impaired toward the high side, consequently 99% capacity is used.

- Attenuation seems high for a site reportedly very close to dslam.

- more than 1% cells are received with CRC errors.

edit: I cannot find a way to set SNR values on the 8xx. You can try "dsl lom 20", but you should enable dsl logging before.

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