[SOLVED] Weird LAN/Wifi issue - must read

[Marcelmmx]

Hello,
In my house I am using a LAN as shown on this simplified drawing.
The primary router 192.168.0.1 is a Netgear D7000 VDSL router with the latest original firmware and the secondary 192.168.0.250 is a TP-Link TL-WR0146ND with DD-WRT v24SP2 (DHCP disabled) – connected via cable and used to improve WiFi coverage upstairs in my house. The switch is an unmanaged Netgear ProSafe 24 port gigabit switch.

When connecting using different wireless devices with both iOS and Android I have the following issue:
If the devices connect via WiFi A on my primary router, they can access the SAT receiver and the NAS without any issues.
When I connect them using WiFi B on my secondary router, both devices can access the SAT receiver and the NAS without any issues.

However, when I now switch back to WiFi A, neither device can access the SAT receiver and the NAS.
They don‘t see the devices on the network and cannot even ping them.
This situation lasts for some 8 minutes and 30 seconds after which the SAT and NAS become pingable and visible from my iOS and Android devices (this applies to all wired devices connected to my switch – all become visible after the said 8 minutes 30 seconds).

If I repeat this process – Wifi A – WiFi B – WiFi A the result is always the same and it takes 8.5 minutes till the SAT receiver and the NAS are visible on WiFi A again.

I have absolutely no idea what can be causing this. There are no other issues with the network, all wired and wireless devices are working properly, the speeds are good, the VDSL connection works fine. The issue now exists over 2 years and in that time the Netgear received several firmware updates, but nothing has changed.
Any advice appreciated.
Marcel

 

[Ralston18]

You are welcome.

Very interesting and intriguing problem.

I tend to lean a bit heavily on "reference" links only because I really have no true way to grasp the entire situation and context. There is always the chance the some such link may lead you to a "Eureka" moment.

As for milliseconds and minutes the difference you are working to resolve ("shave off") is significant.

It may actually be milliseconds but in some sort of repeating loop that eventually works itself out or times out in some manner.

I have spent some time thinking about how I could create such a situation; aka reverse engineering... Some sort of event chain where some wrong information gets corrected but then another device (still wrong) promulgates the wrong information and it all goes in circles. Incorrect following correct.

We have looked at the cable plant, the hardware, the IP addressing, etc. ( And it would have been great if the issue had simply been a faulty switch....)

What is needed is more insight as to what the wireless network is doing (or trying to do) during the delayed handovers.

Would Wire Shark be an applicable tool? Or some similar monitoring utility.

The other approach that I can think of is to take the entire network down and in some TBD methodical manner start adding devices back one by one. At some point the tipping point will be reached the delays re-occur.

Maybe use some monitoring tools to watch the network during each step and action.

Powershell offers a variety of network commands that might prove useful for getting a quick look at what may be going on with respect to any given computer or network. Advanced IP Scanner like information.

Start monitoring as much as possible and force a handover: i.e., " the problem shows up as soon as a wireless device switches from wifi B to wifi A".

It may well be some perfect storm situation. Yet, mixing metaphors, there may a butterfly somewhere.