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Explorer

Poor performance/packet loss with Cisco 887VA router on ADSL line

We have a remote site connected to ADSL line with a Cisco 887VA router attached. This has been working fine for the last couple of months. However, recently, the site have started to complain of performance issues (network slow, applications disconnecting, etc)

Looking on the router, we can see evidence of packet loss/timeouts from a simple ping to the internet e.g.

ping 8.8.8.8 repeat 100

Type escape sequence to abort.

Sending 100, 100-byte ICMP Echos to 8.8.8.8, timeout is 2 seconds:

!!!!..!!!!!!!!!!!!!!.!!!!.!!!!!!!!.!!!.!!!!!!!!!!!!!!!!.!!!!!!.!!!!!!!

!!!!!!!!!!!!!!!!!!!!!!.!!!!!!!

Success rate is 91 percent (91/100), round-trip min/avg/max = 36/38/60 ms

And looking at the “show controller vdsl 0” stats, the Noise Margin seems very low:

sh controller vdsl 0

Controller VDSL 0 is UP

Daemon Status:           Up

                       XTU-R (DS)             XTU-C (US)

Chip Vendor ID:         'BDCM'                   'IFTN'

Chip Vendor Specific:   0x0000                  0x71BE

Chip Vendor Country:   0xB500                   0xB500

Modem Vendor ID:       'CSCO'                   '   '

Modem Vendor Specific: 0x4602                   0x0000

Modem Vendor Country:   0xB500                   0x0000

Serial Number Near:    FCZ1602C128 887VA-K9 15.1(4)M

Serial Number Far:

Modem Version Near:   15.1(4)M

Modem Version Far:     0x71be

Modem Status:           TC Sync (Showtime!)

DSL Config Mode:         AUTO

Trained Mode:           G.992.5 (ADSL2+) Annex A

TC Mode:                 ATM

Selftest Result:         0x00

DELT configuration:     disabled

DELT state:             not running

Trellis:                 ON                       ON

Line Attenuation:       46.0 dB                 25.3 dB

Signal Attenuation:     46.0 dB                 25.6 dB

Noise Margin:             3.6 dB                 6.8 dB

Attainable Rate:       6856 kbits/s             1088 kbits/s

Actual Power:           18.5 dBm               12.8 dBm

Total FECS:             70880096                        608

Total ES:               22041                   44

Total SES:             22041                   0

Total LOSS:             0                       0

Total UAS:             0                       0

Total LPRS:             0                        0

Total LOFS:             0                       0

Total LOLS:             0                       0

Bit swap:               7946                     23

Full inits:             1

Failed full inits:     0

Short inits:           0

Failed short inits:     0

Firmware       Source         File Name (version)

--------       ------         -------------------

VDSL           user config     flash:vdsl.bin.32bdslfw (10)

Modem FW Version:     101028_1158-4.02L.03.A2pv6C032b.d23b

Modem PHY Version:     A2pv6C032b.d23b

                 DS Channel1     DS Channel0   US Channel1       US Channel0

Speed (kbps):             0             5658             0             1062

Previous Speed:           0               0             0                0

Total Cells:             0       299125688             0         55976223

User Cells:               0         6570139             0           343547

Reed-Solomon EC:         0         70915190             0               608

CRC Errors:               0         1370201             0                 0

Header Errors:           0         6272974             0               77

Interleave (ms):       0.00             7.96         0.00             5.98

Actual INP:           0.00            1.01         0.00             0.46

However, we have logged the fault with our service provider and they return all line tests as clear but what is particularly strange is that they also report “and the SNR Margins are well within threshold levels (Upstream 11.5 and Downstream 15.0)” which, unless I’m misunderstanding something, seems to be completely different from what the router itself is reporting.

Is there a reason why the service provider’s stats for Noise Margin would appear to be so different from what the router is reporting?

And can anyone suggest any way we might a) identify the root cause of the issue and b) resolve it?

Thanks.

2 REPLIES 2
Hall of Fame Master

Poor performance/packet loss with Cisco 887VA router on ADSL lin

Circuit shows high attenuation and poor SNR.

Try another router if possible.

Explorer

Poor performance/packet loss with Cisco 887VA router on ADSL lin

Hi,

just to update on this one.  This has now been resolved after an engineer from the telco visited the site (we are told it was an "exchange fault" but not much more detail than that unfortunately.  We did not need to replace our router so it was definitely an issue on the telco side.  I believe the reason for the discrepancy between the noise margin reported by the Cisco router and that reported by the service provider was that they ran their diagnostics on the wrong line! (this ADSL line was in our office above the branch - they ran diagnostics against the branch connection)

Thanks for your input all the same.

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