Avoiding Routing Interruption During Transition to a Virtual Entity

An edge router within a topology transparent zone (TTZ), comprising:

• an input/output (I/O) device configured to receive and transmit packets between edge routers;
• and
• a processor operably coupled to the I/O device and configured to:
• virtualize a path from an edge router to another edge router within the TTZ in a first direction without removing original links, wherein the original links are links from the edge router to its neighboring routers within the TTZ;
• receive a router link state advertisement (LSA) from the another edge router within the TTZ while the original links remain in place, wherein the LSA comprises a path from the another edge router to the edge router in a second direction different from the first direction;
• and
• remove the original links after the LSA has been received from the another edge router and the virtualization of the path is complete to transition to the TTZ.

A method of smooth migration to a topology transparent zone (TTZ) for routers having a TTZ feature enabled, comprising:

• distributing, by a first router, first router TTZ information to a second router neighboring the first router, wherein the first router TTZ information includes a first TTZ control advertisement configured to trigger the second router to distribute neighbor router TTZ information to a third router neighboring the second router;
• migrating, by the first router, to TTZ functionality and distributing additional first router TTZ information to the second router, wherein the additional first router TTZ information includes a second TTZ control advertisement configured to trigger the second router to migrate to the TTZ functionality and to distribute additional neighbor router TTZ information to the third router;
• and
• removing, by the first router, original links between the first router and the second router after migration of the first router to the TTZ functionality.