Abstract: A network node comprising a receiver and a processor is disclosed. The receiver is configured to receive an identifier of an intermediate-system-to-intermediate-system (ISIS) topology-transparent-zone (TTZ) to which the network node has been assigned, further configured to receive and store ISIS TTZ topology information, and further configured to receive an indication to distribute topology information related to the ISIS TTZ to other network nodes assigned to the ISIS TTZ. The processor is coupled to the receiver and configured to generate a TTZ-related type-length-value (TLV) and set an indicator in the TTZ-related TLV to indicate that topology information related to the ISIS TTZ is to be distributed, add the TTZ-related TLV to TTZ-related information associated with the network node, and initiate distribution of the TTZ-related information to all TTZ nodes adjacent to the network node.