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'ADSL show' commands


'ADSL show' commands

Been playing with the various 'ADSL show' commands using telnet on my SAR715+ router.

Does anyone know what the 'show error' command results actually mean?
Both upstream and downstream give values for FEC, CRC and HEC which look quite large to me but on the other hand I have no problem with my connection. What do FEC,CRC and HEC stand for? Any info appreciated.
My values are given as:
FEC: 65535
CRC: 352
HEC: 178

FEC: 65529
CRC: 65531
HEC: 65528


'ADSL show' commands

Wow, they are very high.

FEC/HEC and CRC errors are counters showing how many times your router has counted bad data.

For each packet of data sent, a checksum is sent. These checksums are calculated from the data about to be sent, and when computed on the otherside, it should match. When it doesn't, you get an error.

FEC/HEC are link level. This means they relate to the actual signal sent and received in the DSL link.

CRC are errors in the data being transmitted.

You never get a 0 count of CRC errors where HEC/FEC errors are apparent, though you can get CRC errors without HEC/FEC.

Based on those counts, I sugest the following.

1: Power cycle your router. May not be what you want, but you need to fully reset the router.

2: Once per 24 hours, issue a "show errors". Take note of the values, and we can calculate a 24 hour average.

3: Post the 24 average

It is upto you how many days you do this for.

The fact these values are so high, could be a counting error in the firmware. So this check can rule that out.

As a rough guide, on the two account I can monitor, I see roughly 12 errors in total (HEC+FEC+CRC) over a month. AKA, it should be low, but doesn't need to be that low.

Moe immidiate things you can do is to read the ADSL: Trouble Shooting and ADSL: Wiring and Filters FAQ's and Tutorials.

'ADSL show' commands

Thanks for the info and advice.

Will do as you suggest and keep a log of the performance figures after resetting my router every day or so and see what the results look like. If the figures are so high and there is a problem somewhere why does it not affect my connection in real time? Anyway will wait and see and take things one step at a time.

'ADSL show' commands

Noticed that even resetting my router, the figures came back high again within the hour. So as you suggest may be a counting error problem in the router.
Finaly decided to start the router back from orginal default start up with all entries re-set. Inputted all my relevant ADSL start up values and now figures all appear to be staying low. Have had it on over 24 hours and figures seem OK now. WIll keep a log and see how things go.
Values for various 'ADSL show' commands listed below for info.

--> adsl show error
Downstream :
FEC : 0
CRC : 17
HEC : 7
Upstream :
FEC : 0
CRC : 0
HEC : 0

--> adsl show perf
Downstream :
Noise Margin : 33.5 dB
Attenuation : 38.5 dB
Output Power : 17
Upstream :
Noise Margin : 14.5 dB
Attenuation : 20.5 dB
Output Power : 9

--> adsl show rate
Data Path : Fast
Downstream Bit Rate : 576 Kbps
Upstream Bit Rate : 288 Kbps

--> adsl show defects
Downstream :
No defects
Upstream :
No defects

'ADSL show' commands

Well, the Attuation is very good, and the noise margin apears OK.

Give it a week and work out the total HEC and CRC errors. This should give you an idea of any paticular problem now.

As for them going high quick, it could well be that the router was never reset to factory defaults after a newer firmware was applied.

In which case, old memorry addresses may have been in use.