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 220.127.116.11 repeat 100
Type escape sequence to abort.
Sending 100, 100-byte ICMP Echos to 18.104.22.168, 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?
Circuit shows high attenuation and poor SNR.
Try another router if possible.
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.