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ferdytao
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RB951Ui-2HnD - Ether1 burns my devices

Mon Sep 26, 2016 9:04 am

Hi to all Mikrotik's useres,
I'm writing here because since a couple of days I have a problem with my mikrotik which is driving me to crazy!!
Since once I bought it the ether1 was a bit difficoult to let it work. I have my ISP modem/router connected to ether1 as dhcp client, the port stay always as active with 512b of traffic TX and RX but it doesn't get the address from the modem. If I configure the dhcp on one of the other ports it works so I don't think is a problem of the ISP modem.

No it's happened a strange and scary thing, after I updated to 6.37, following the reboot the device stopped to get the address and plugging in and out the cable from the modem to the mikrotik and rebooting the mikrotik several times, the cable on modem side started to smoke and small like burned!!!! :O

I tried to connect the mikrotik to another device always from the ether1 and started the smell of burn also to the new modem. I really don't know what to do now!! Could this be caused buy the POE-IN feature on ther1? I think there is no power on POE-IN!!!

Please help me I have the connection of the whole building limited because I had to use a Mikrotik mHap as a main router and I don't think is strong enough to resist more days.

Thanks for all your suggestions
 
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pukkita
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Re: RB951Ui-2HnD - Ether1 burns my devices

Mon Sep 26, 2016 11:13 am

How are you powering it?

Do you have a multimeter? if so, measure AC/DC from RB951 ethernet metallic frame to ground, could be a defective power unit/strip causing an electric shunt, there's nothing on the 951 per se that could damage another unit, less on its ether1 (PoE-in) port, unless its internally damaged.

This unit case is easy to open, open it and have a visual inspection (or post good resolution photos from both sides here)

Which kind of cables are you using? are they shielded? do they have drain wire?
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Re: RB951Ui-2HnD - Ether1 burns my devices

Mon Sep 26, 2016 12:01 pm

Did you force POE to be on, on that interface?
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pukkita
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Re: RB951Ui-2HnD - Ether1 burns my devices

Mon Sep 26, 2016 12:17 pm

RB951-Ui is PoE-Out only on ether5. ether1 is PoE-In.
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ferdytao
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Re: RB951Ui-2HnD - Ether1 burns my devices

Mon Sep 26, 2016 12:36 pm

How are you powering it?

Do you have a multimeter? if so, measure AC/DC from RB951 ethernet metallic frame to ground, could be a defective power unit/strip causing an electric shunt, there's nothing on the 951 per se that could damage another unit, less on its ether1 (PoE-in) port, unless its internally damaged.

This unit case is easy to open, open it and have a visual inspection (or post good resolution photos from both sides here)

Which kind of cables are you using? are they shielded? do they have drain wire?
Ciao Pukkita,
thanks for your prompt replay, i opened the case and the board looks in good condition, I will try with a multimeter once I will be back home and I will update you, I ordered a new one because my network is under pressure now but I hope I could find a solution.

I suppose it could be internally damaged as you said, I used a normal cat5e cable not shielded. Actually I had several problem with this port because it was used to don't get the dhcp address so easily and the led on the board kept on even if the cable us unplugged.
Going on "cable test" with winbox it says connected even when there is no cable connected on it!

Maybe I have just to throw it! :D
 
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pukkita
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Re: RB951Ui-2HnD - Ether1 burns my devices

Mon Sep 26, 2016 1:53 pm

Mmmm... that could indicate a damaged port, if ether1 isn't the master for any other port. Have you tried another port in the mean time?

It could just come damaged, or it could have been damaged by something in your installation, that's why I advised to doublecheck prior to plugging another router to prevent damaging it in the event of having stray electricity shunting somewhere.

How do you power it? by the DC jack I guess?
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Re: RB951Ui-2HnD - Ether1 burns my devices

Mon Sep 26, 2016 2:00 pm

Or check what voltage is on each pin of Eth1 port. Use "octopus" made from a spare connection cable or better the one which you do not need, cut it to have RJ45 connector and a few cm of cable left, unstrip each line and check it for over voltage or short circuts.
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ferdytao
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Re: RB951Ui-2HnD - Ether1 burns my devices

Mon Sep 26, 2016 2:02 pm

Mmmm... that could indicate a damaged port, if ether1 isn't the master for any other port. Have you tried another port in the mean time?
Ether1 is the wan port itself, the ether2 is the master for the 3 and 4. If i try to connect the ISP modem to ether2 configured with dhcp client it get the address without problem.
It could just come damaged, or it could have been damaged by something in your installation, that's why I advised to doublecheck prior to plugging another router to prevent damaging it in the event of having stray electricity shunting somewhere.
I will try as you said with a multimeter before proceeding with another device.
How do you power it? by the DC jack I guess?
Yes by the DC power supply.
 
ferdytao
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Re: RB951Ui-2HnD - Ether1 burns my devices

Mon Sep 26, 2016 2:07 pm

Or check what voltage is on each pin of Eth1 port. Use "octopus" made from a spare connection cable or better the one which you do not need, cut it to have RJ45 connector and a few cm of cable left, unstrip each line and check it for over voltage or short circuts.
Thanks for your suggestion I will try once I will be back home
 
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Re: RB951Ui-2HnD - Ether1 burns my devices

Mon Sep 26, 2016 6:34 pm

Maybe is a damage router returned for replacement and the seller tried to make a good business with you.
 
ferdytao
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Re: RB951Ui-2HnD - Ether1 burns my devices

Thu Oct 06, 2016 1:05 pm

I checked the ether1 with a multimeter, it goes to ground that's the problem. I can still use the router without the ether1, just disabled to be sure ;)

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