How to add route with busybox (for specified destination and gateway)
Magisk:

/dev/busybox/route add -net 1.0.1.0 netmask 255.255.255.0 gw $(getprop net.dns1)

Busybox:

/system/xbin/busybox route add -net 1.0.1.0 netmask 255.255.255.0 gw $(getprop net.dns1)