ip route show table 127 gives me
192.168.0.0/24 dev eth0 proto static
default via 192.168.101.3 dev tap0 proto static scope link
To change it, do
ip route replace default via x.x.x.x dev tap0 table 127
Routing for a while has been using the ip_route2 programme which uses these tables.
ip rule list will give you the active rules and the tables they use.
Tables are usually in /etc/iproute2/rt_tables...