I have private APN with few sim cards. In the old days NetworkManager created ppp connection with my modem and then I've run
ip route add 10.9.200.0/24 dev ppp0 (or add routing via NM)
And every packet with such destination network was traveling via such Point To Point interface.
Now with WWAN when I add routing without gateway
ip route add 10.9.200.0/24 dev wwan0 (or add routing via NM)
and get tcpdump on such interface I've got arp requests for destination host and that's it :-/
How to get things working under NM with WWAN ?