Re: [lwip-users] Losing connection with router

[Mike He]

I will order a hub and set up a capture. But in the meantime, I'm trying 
to narrow down whether the problem stems from my device running lwip, or 
the router.

If the device can still be pinged, then it clearly should still be in 
ARP table. However, the router management interface lists no record of 
it, and the connection out of the router was definitely broken off and 
cannot be resumed. Meanwhile, a raspberry pi on the same router does not 
have this problem, and another instance of my device on a different 
network (fiber-connected office router) also does not have this problem. 
So, this leaves me perplexed as to why this particular device with this 
router drops connectivity while still being on the ARP table, and can no 
longer be reached again. Any ideas are welcome. If no suggestions can be 
made from this information, that is fine, I will post a capture at a 
future time and hopefully that will clarify.

Mike

On 2/24/2016 10:53 AM, Sergio R. Caprile wrote:
> I don't understand what you say, routers do not "recognize devices",
> they resolve IP addresses to MAC addresses via ARP like any other host
> in a network and route IP datagrams based on IP addresses.
>
> If you can ping your lwIP device, then it is probably alive.
> If the router does not show it in "the list of connected hosts", then
> you have to understand what that "list of connected hosts" is and what
> is the merit of one to get to that honour, because your device is
> probably not up to it. Your router is quite likely more than a router
> and you are not paying attention to a requirement for connectivity.
>
> Please (indeed), do yourself a favour and capture the network traffic,
> so you can see why you lose your connection; and learn about that router.
> You'll be able to see DHCP lease times, renewals, and all that stuff
> while looking at the capture file. It is a bit of more use than guessing
> in the dark.
>
> You'll need a hub, or a switch with "monitor mode" to capture both lwIP
> device and router traffic in that network. See this:
> https://wiki.wireshark.org/CaptureSetup/Ethernet
>
> If the RBPI works OK, and you can't get info on the router, then leave
> the RBPI running and capture its traffic too.
> If you are planning to post that capture file later, please be nice and
> set a small network aside with a switch so we don't get to see the whole
> network traffic...
>
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