The IGP-LDP synchronization and the static route-to-LDP synchronization features are modified to operate on a dual-stack IPv4 or IPv6 LDP interface as follows.
If the router interface goes down or both LDP IPv4 and LDP IPv6 sessions go down, IGP sets the interface metric to the maximum value and all static routes with the ldp-sync option enabled and resolved on this interface are deactivated.
If the router interface is up and only one of the LDP IPv4 or LDP IPv6 interfaces goes down, no action is taken.
When the router interface comes up from a down state, and the LDP IPv4 or LDP IPv6 sessions comes up, IGP starts the sync timer. When the sync timer expires, the interface metric is restored to its configured value and all static routes with the ldp-sync option enabled are activated.
Given the above behavior, it is recommended that the user configures the sync timer to a value that allows enough time for both the LDP IPv4 and LDP IPv6 sessions to come up.