[PLUG] How best to connect a subnet of Pi Zeros?

Eric House eehouse at eehouse.org
Wed Jan 20 01:32:44 UTC 2021


You may be able to bridge your usbN interfaces, but not with a wifi
> client interface. I'd plug them into a USB bus on a device with a
> wired connection to the DHCP server.
>

(Monospaced font required)

So here's my network now.

     WAN
      |
+------------------+
| Ubiquity X       |
| running OpenWRT  |
|   (w/Switch      |
|  10.43.21.1)     |
+------------------+
     |
     | <- single Cat5e cable running length of the house
     |
  +------------------------+
  |  Switch in my office   |
  +------------------------+
   |           |         |
+-----------+  |         |
| Desktop 1 |  |         |
+-----------+  |       +------------------------+
               |       |   Pi4 running OpenWRT  |
      +-----------+    | with USB<n> bridged    |
      | Desktop 2 |    | into a DMZ 192.168.2.1 |
      +-----------+    +------------------------+
                           |        |       |
 USB OTG connections ->    |        |       |
                        +-----+  +-----+  +-----+
 Raspberry Pi Zeros ->  | PZ0 |  | PZ1 |  | PZn |
                        +-----+  +-----+  +-----+

Right now the Zeros are getting grouped into a bridge with addresses
correctly assigned within the 192.168.2.255 range by a local DHCP
server on the Pi4. They can see each other's hostnames, ssh to each
other, etc. As can anything else I plug into the Pi4. But from my
desktops I can't see them: their names don't make it to the Ubiquity
X's DNS, nor does that router know how to route 192.168.2.<n>
addresses. The Zeros can't see the names of my desktops, but they can
ping them by ip address: apparently the Pi4 sends 10.43.21.n addresses
upstream when it can't resolve them itself.

This doesn't surprise me, and I'm pretty sure I can fix the two
routers to work together. Just not sure that's the right way to
proceed. What I want is to be able to route http[s] traffic from the
WAN down to the Zeros (with something in between -- maybe the Pi4
itself) doing some sort of load balancing.) And I definitely want my
desktops to be able to ssh and http to the Zeros by name.

As I think about this, I want the Pi4 to appear on the Ubiquity in a
separate zone (a DMZ I guess). That'd be trivial if they were joined
by a dedicated cable, but all traffic reaches the Ubiquity through the
same physical port. Seems though that I should be able to create a
tunnel between the two and put that in a separate zone on the
Ubiquity. I've started reading in that direction. Suggestions
welcomed!

Once I figure out how the subnet shows up on the main router I can
look at moving all DHCP and DNS there if that still makes sense.

Thanks,

--Eric


-- 
My g-bike can trounce your e-bike!



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