[kwlug-disc] Networking issue

[Khalid Baheyeldin]

I have this rare problem that is extremely annoying when it happens.
Basically, I have two routers. R1 is the main home router, connected
to the internet, managing DHCP, and so on. The other router, R2, has
no DHCP, and is simply for range, as well as a couple of RJ45 devices,
due to proximity to those devices.

Some WiFi devices that report temperature, humidity, ...etc. report
to R2 due to better range. A Raspberry Pi is connected to R2 directly
using RJ45. The Pi and the WiFi devices have static IPs in R1 served
using DHCP.

On rare occasions, the WiFi on R2 misbehaves. I can still ssh into the
Pi, but the WiFi devices have trouble reporting to the Pi. The solution
is to reboot the routers. Doing so makes WiFi more stable, but then
the Pi is inaccessible over ssh or HTTP. I have to cycle power to the
Pi, and I hate doing that since it may corrupt the file system on the
SD card.

Even when reboot both routers and cycle power, the Pi is not accessible
still. Pings fail, let alone ssh. Don't know why.

The only clue I can find is that when I use arp (from R1), the Flags
column for the Pi is 0x0 while it is 0x02 for all other devices.

I tried to delete the arp entry for the Pi, using this, from a Linux
machine:

arp -d 192.168.0.x
arp -s 192.168.0.x b8:27:xx

After that, I see this:

Address HWtype  HWaddress           Flags Mask            Iface
zz           ether       b8:27:xx                CM                    eth0

Again, the Flags column is CM, while it is C on other devices.

How can go about troubleshooting this extremely annoying problem?
-- 
Khalid M. Baheyeldin
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