In an MPLS network with L3VPNs, it's very easy for the NEXT_HOP attribute of a VPN route to look absolutely correct but be very wrong at the same time. In a vanilla IP network, the NEXT_HOP can point to any IP address that gets the packets moving in the right direction towards the ultimate destination. In an MPLS network, the NEXT_HOP must get the packets moving in the right direction but it must also point to the exact right address in order for traffic to successfully reach the destination.
