Try: https://cloudflare.com/cdn-cgi/trace
I do this:
# in /etc/config/network
config route
option interface 'foo_warp1'
option target '0.0.0.0/0'
option table '1'
config rule
option src '192.168.1.0/24'
option dest '0.0.0.0/0'
option priority '1' #order in IP_rules
option lookup '1' #table_assigned
Some use a PBR package.
(If you want to name the table, it requires extra config.)