Debugging link negotiation problem with Linksys E8450 / Belkin RT3200?

I have a strange problem since yesterday: my RT3200 does not properly negotiate link with the ISP's fiber cabling since a thunderstorm yesterday.

Key facts:

  • modern apartment house with ISP fiber to cellar, RJ-45 CATx endpoint in my apartment.
  • RT3200 worked ok since yesterday morning. Then there was a major thunderstorm during the day. Lightning hit a tree right next to the house. Persons from several apartments have had internet breakage...
  • Since that the RT3200 does not properly form (gigabit) link with the ISP hardware in cellar. Kernel log shows that the wan link "1 Gbit full duplex" gets established. But it is lost after one second. After two seconds, the link is renegotiated, but is then lost after one more second. This 1-2-1-2-1-2 rhytm continues forever, quite steadily. (actually 1.03 seconds on - 2.0x seconds off - 1.03 seconds on - ...)
  • If RT3200 wan is connected to my R7800's LAN port, the link gets formed ok. So RT3200 wan port is able to negotiate with some hardware
  • R7800 and my PC do get the link with the ISP.
  • ISP technical support remotely checked the connections, and if R7800 (or the PC directly) is connected to the ISP cabling, everything seems ok. But if RT3200 is connected, they see some errors. Their judgement was that likely it is about the RT3200 hardware.

Possibly the RT3200 wan port has somehow fried, but still works with some opposing hardware?

Hardware link negotiations are not my strong suit, so I am a bit baffled how to debug the situation?

Ps. I had to also power-off a dumb switch in order to restore fixed connections to other devices rooms in the apartment. The switch was connected to RT3200 during the thunderstorm. That increases my belief that there has been some electric spike, at least to RT3200 but also reaching the switch to some extent...

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Two things coming to mind that might be worth checking.

  • putting a switch between ONT and rt3200 WAN
  • redefining a LAN port of your rt3200 as WAN interface

If the onboard switch or the CPU port of the rt3200 is shot, neither is likely to work, but the test results might still provide some hints.


While I think that hardware is permanently damaged does it keep link if you use one of the LAN-ports?


Thanks for the ideas.

Luckily, it proved to be something in the ISP hardware in cellar after all. One of the other residents managed to get an ISP representative to visit the cellar and change/fix/reset/reboot some equipment there. Now the RT3200 again gets link and nicely manages 200/60 Mbit connection.

Ps. Just for fun:
Photo of the pine next to the house. Note the vertical line of thunderbolt damage in the bark, and the exploded bark pieces on the ground.


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