Internet connection redundancy (DSL and 4GLTE)

[BERTRAND Joël]

        Hello,

        For a long time (9 months), my DSL connection is unstable. Thus, I have
bought last Saturday a 4G Ethernet modem. Now, my WAN connection is :

wm2 (192.168.15.14)
  +---- DSL modem (Archer VR400, 192.168.15.20)
  +---- 4G modem (TL-MR6400, 192.168.15.19)

        Now, I'm trying to automatically change default route (from
192.168.15.20 to 192.168.15.19 and reciprocally) when DSL connection is
down.

        Is there a mechanism to do this with NetBSD ?

        Best regards,

        JKB