Route leaking allows L2 LSPs to be sent into L1 areas. Route leaking is configured with the command:
configure isis area area_name interlevel-filter level 2-to-1 [policy | block-all | allow-all] {ipv4 | ipv6}
The supplied policy defines what route or routes should be leaked.
Caution
Route leaking can reduce scalability and performance.
Note
Tracert does not work if the VRF leaked route is one of the hop(s) to destination.