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Posts: 69
Joined: Fri Jun 02, 2006 3:48 pm

long distance link keeps dropping

Tue Oct 20, 2009 7:39 pm

HI Guys

Maybe someone can help me here

We have a tower with 2 antenna pointing to 2 diffrent directions, about 40-50 KM, both side equipment is the same

the grids is 31 DBI with R52H on both sides with VP, boards is 433AH

We have a good -70 signals, and nstreme is enabled, RouterOS versions is 3.30

Every few minutes, can be few hours as well, The link suddenly drops and comes back up

We have tried superchannel license with every possible frequency, also changed channel width to see if makes difference, but no luck

Nstreme disabled also makes no difference, doing a bandwidth test i get 15mbits each way, so speed is there

I have tried setting the disconnect timeout to 10s to see what happens, but still drops

Also tried 433AUH board with some other radios , that DBii Networks 802.11a High Power Card with RF Line Protection , but still no change

Also verified with installers we have clear LOS and antennas not to close to each other, ALso we in the middle of nowhere , not much on the tower but us

What could be wrong here?


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Posts: 14
Joined: Fri May 29, 2009 9:21 pm

Re: long distance link keeps dropping

Thu Oct 22, 2009 4:50 pm

Please tell me is this problem from the begining or did it suddenly statred?
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Posts: 69
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Re: long distance link keeps dropping

Thu Oct 22, 2009 6:28 pm

almost from the beginning, on nstreme Disabled i had alot of duplicate packets, once nstreme enabled, the link became stable

we then had power issue at tower which we sorted out

i see the links very sensitive to dropping, its stays up for hours , then if i work on the other link which is dropping alot, then the more stable one suddenly drops and comes back up

I however have alot of mpls running on there with ospf, but this shouldnt be any problem

i had a look at my stats on the reg table to the more problem link

tx-ccq=78% rx-ccq=76%

could this be something on the tower thats causing it, some kind of bigger telco kit?, we considering changing tower as we had some strange problems on this site with power( we have ups) and the links is 50km+


Posts: 30
Joined: Sun Sep 16, 2007 10:24 pm

Re: long distance link keeps dropping

Sun Oct 25, 2009 10:08 am

Try to swap R52H with R5H (if you need little more dB) or use old good CM9.
We have some long links with R52H and have same problems until changing radio cards.
Posts: 311
Joined: Thu May 31, 2007 12:38 am

Re: long distance link keeps dropping

Sun Nov 01, 2009 10:00 pm

You SNR is no good for reliable link... u need min 25db..

Your noise level must be high on the tower.

Maybe your radio card is defunct.
Posts: 316
Joined: Tue Mar 01, 2005 1:59 pm
Location: Serbia

Re: long distance link keeps dropping

Mon Nov 02, 2009 7:40 am

If you hardware retries set to 4 try to change hardware retries to 15 or maybe litter higher. I also have link 25km signal -80, with connect disconnect every couple minutes after changing hardware retries to 15 have up time couple of days.

From manual:
* hw-retries (number 0..15; default value: 15) : Number of times sending frame is retried without considering it a transmission failure.

Data rate is decreased upon failure and frame is sent again. Three sequential failures on lowest supported rate suspend transmission to this destination for the duration of on-fail-retry-time. After that, frame is sent again. The frame is being retransmitted until transmission success, or until client is disconnected after disconnect-timeout. Frame can be discarded during this time if frame-lifetime is exceeded.
On my router default value is 4.

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