Running debian on a pi3.
I can switch between eth0 and ppp0 to reach the internet but only one interface can be active at a time. Of course this is because the Linux OS manages the default gateway and routing tables when an interface is taken down. Such as:
ifconfig eth0 down
This prevents me from checking the cable modem on eth0. I'd like to have both physical interfaces up but when the cable modem internet becomes unresponsive, I'd like to send out http data (json) over the ppp0 interface. I'd also like to periodically ping over the ppp0 interface to verify it's working as well.
My lack of network routing, etc. is beyond my ability to even search for the answers! I'm guessing I need to modify routing tables and determine how to force IP out over a specific interface from python code.
Any suggestions welcome.