Method to achieve the use of an external metric as the primary tie-breaker in intermediate system to intermediate system (ISIS) route selections
View Patent ↗A method, apparatus and computer program product for providing the use of an external metric as the primary tie-breaker in ISIS route selections is presented. A set of routes are identified that are to be advertised by the router as external routes within a network. The routes are advertised by the router using a Type Length Variable (TLV), wherein the TLV contains metric information to be used as a first tiebreaker when selecting routes. The network is running an Intermediate System To Intermediate System (ISIS) protocol. The TLV includes a 32-bit or a 64-bit administrative tag sub-TLV, the TLV comprising TLV#135, TLV#235, TLV#236, and TLV#237.
1. A computer-implemented method in which a router performs operations comprising:
receiving, at said router, route advertisements within a network;
determining for a route advertisement if a particular administrative sub-TLV is present in said route advertisement;
when said particular administrative sub-TLV is present in said route advertisement then using metric information in said TLV for said route as a first tie-breaker when selecting between routes; and
when said particular administrative sub-TLV is not present in said route advertisement then using internal ISIS Layer 1 (L1) cost as the first tie-breaker when making a route selection.
2. The method of claim 1 wherein said network is running an Intermediate System To Intermediate System (ISIS) protocol.
3. The method of claim 1 wherein said TLV is selected from the group comprising TLV#135, TLV#235, TLV#236, and TLV#237.
4. The method of claim 1 wherein said TLV includes at least one of the group comprising a 32-bit administrative tag sub-TLV and a 64-bit administrative tag sub-TLV.
5. A non-transitory computer readable storage medium having computer readable code thereon for providing use of an external metric as a primary tie-breaker in route selections, the medium including instructions in which a router performs operations comprising:
receiving, at said router, route advertisements within a network;
determining for a route advertisement if a particular administrative sub-TLV is present in said route advertisement;
when said particular administrative sub-TLV is present in said route advertisement then using metric information in said TLV for said route as a first tie-breaker when selecting between routes; and
when said particular administrative sub-TLV is not present in said route advertisement then using internal ISIS Layer 1 (L1) cost as the first tie-breaker when making a route selection.
6. The computer readable storage medium of claim 5 wherein said network is running an Intermediate System To Intermediate System (ISIS) protocol.
7. The computer readable storage medium of claim 5 wherein said TLV is selected from the group comprising TLV#135, TLV#235, TLV#236, and TLV#237.
8. The computer readable storage medium of claim 5 wherein said TLV includes at least one of the group comprising a 32-bit administrative tag sub-TLV and a 64-bit administrative tag sub-TLV.
9. A router comprising:
a memory;
a processor;
a communications interface;
an interconnection mechanism coupling the memory, the processor and the communications interface; and
wherein the memory is encoded with an application providing use of an external metric as a primary tie-breaker in route selections, that when performed on the processor, provides a process for processing information, the process causing the computer system to perform the operations of:
receiving, at said router, route advertisements within a network;
determining for a route advertisement if a particular administrative sub-TLV is present in said route advertisement;
when said particular administrative sub-TLV is present in said route advertisement then using metric information in said TLV for said route as a first tie-breaker when selecting between routes; and
when said particular administrative sub-TLV is not present in said route advertisement then using internal ISIS Layer 1 (L1) cost as the first tie-breaker when making a route selection.
10. The router of claim 9 wherein said network is running an Intermediate System To Intermediate System (ISIS) protocol.
11. The router of claim 9 wherein said TLV is selected from the group comprising TLV#135, TLV#235, TLV#236, and TLV#237, and wherein said TLV includes at least one of the group comprising a 32-bit administrative tag sub-TLV and a 64-bit administrative tag sub-TLV.