But IPv6 doesn't really have a route cache either. However, it handles exceptions differently than IPv4. With IPv6, exceptions are put in the tree along regular entries (there has been some bugs, like /128 routes disappearing due to a "cached" entry being expired) while IPv4 stores the exceptions with the next-hop information.
EDIT: I stand corrected: before 4.2, route entries were created for almost any destination, so it was essentially a route cache. After that, the entry is created only when it is really needed (MTU lower than the default MTU).
But IPv6 doesn't really have a route cache either. However, it handles exceptions differently than IPv4. With IPv6, exceptions are put in the tree along regular entries (there has been some bugs, like /128 routes disappearing due to a "cached" entry being expired) while IPv4 stores the exceptions with the next-hop information.
EDIT: I stand corrected: before 4.2, route entries were created for almost any destination, so it was essentially a route cache. After that, the entry is created only when it is really needed (MTU lower than the default MTU).