On 2020-05-24, David Taylor  wrote:
> I recently had an RPi where the Wi-Fi wouldn't connect after a
> power-down reboot.  No settings were changed, and I could see DHCP
> requests going out.  Didn't have the time to resolve it, so used
> Ethernet instead as a connection was to hand.  Other RPi cards on the
> same network have rebooted with power-down multiple times without problems.
>
> However, I've just had a second RPi with the same problem (and same
> solution).  No configuration change, but no Wi-Fi connection.  These RPi
> are both model 1B.
>
> One other change has been adding a second access point (2 GHz) with the
> same SSID.  I've read that this is OK and the device will simply pick
> the strongest signal and connect to it.  Certainly the 5 GHz devices
> such an a iPad, RapPi-4B and Pixel 3 phone.  don't seem to be affected
> (different SSID).  I'm using a separate router connected to my wired
> LAN, and the two access points are connected to that LAN.  No combined
> ISP modem/router/Wi-Fi box involved

The SSIDs are a blind alley IMHO.  Multiple AP networks seem to
have some mystery about them in the hobbyist community where they're
regarded as esoteric, but these things are designed for enterprise
deployment - AP selection and indeed handover were baked into the
spec on day one and essentially work automatically.  I'd look a
bit deeper into the network configuration.

How are the two routers connected?  For a single, seamless network
you would generally want to connect them LAN port to LAN port with
ethernet.  With consumer level gear if you want another configuration
- e.g the second router as repeater - you're probably best with an
actual AP as opposed to a second router since they are generally
slightly more flexible in their bridging options.

What does the new router's IP setup look like?  I suggest a static
IP assignment clear to any DHCP pool but with the same network
address and and match.  Obviously the IP assigned needs to differ
from the first router.  Default route should be the first router
assuming that is where internet connectivity comes from, but
shouldn't be too important since you're essentially using it as a
layer 2 device - that is it's knowledge of IP should be basically
dormant.

In terms of DHCP the simplest way is simply to disable it on the
second router in which case the first will supply addresses to both
APs (assuming that it was supplying the addresses in the first
instance).  A simple form of fault tolerance can be provided by
adjusting both routers to supply from non-overlapping pools in the
same subnet, e.g. 192.168.0.64/27 for the first and 192.168.0.96/27
for the second, assuming a 192.168.0.0 base address.  That way leases
are still assigned if either router is powered down or hung.  I'd
only play with that after the network is working, though.

Finally, just one clarification, can you explicitly confirm the Pi
is not getting a lease of any form over DHCP, not that it is
getting one that does not provide connectivity?

--
Andrew Smallshaw
andrews@sdf.org

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