ip route delhas the same arguments as
ip route add, but their semantics are a bit different.
Key values (
select the route to delete. If optional attributes are present,
verifies that they coincide with the attributes of the route to delete.
If no route with the given key and attributes was found,
ip route del
Linux-2.0 had the option to delete a route selected only by prefix address,
ignoring its length (i.e. netmask). This option no longer exists
because it was ambiguous. However, look at ip route flush
(sec.7.4, p.) which
provides similar and even richer functionality.