The value of vRtrMplsP2mpInstMBBFailNodeAddr indicates the IP address
of the node in the P2MP LSP path at which the in-progress MBB failed.
A value of 'unknown' for vRtrMplsP2mpInstMBBFailNodeType and empty
string for vRtrMplsP2mpInstMBBFailNodeAddr indicates that no failure
has occurred.