Maintaining IGP transparency of VPN routes when BGP is used as a PE-CE protocol

• US 20070260746A1
• Filed: 05/08/2006
• Published: 11/08/2007
• Est. Priority Date: 05/08/2006
• Status: Active Grant

• Current Assignee: Cisco Technology, Inc. (Cisco Systems, Inc.)
• Original Assignee: Cisco Technology, Inc. (Cisco Systems, Inc.)
• Inventors: Mirtorabi, Sina, Psenak, Peter, Rosen, Eric, Shaikh, Mukhtiar
• Granted Patent: US 7,865,615 B2
• Time in Patent Office: Days
• US Class Current: 709/238
• CPC Class Codes: H04L 12/66 Arrangements for connecting between networks having differing types of switching systems, e.g. gateways
• CPC Class Codes: H04L 45/02 Topology update or discovery
• CPC Class Codes: H04L 45/033 by updating distance vector protocols
• CPC Class Codes: H04L 45/04 Interdomain routing, e.g. hierarchical routing
• CPC Class Codes: H04L 63/0272 Virtual private networks

Abstract

A technique maintains Interior Gateway Protocol (IGP) transparency of Virtual Private Network (VPN) routes when Border Gateway Protocol (BGP) is used as a Provider Edge Device (PE) to Customer Edge Device (CE) protocol in a computer network. According to the novel technique, a first CE generates a BGP advertisement to advertise one or more VPN routes of its customer network, the BGP advertisement having one or more transitive IGP attributes for the advertised routes. The first CE sends the BGP advertisement to a first PE, which then propagates the BGP advertisement among devices of a provider network maintaining the transitive IGP attributes. A second PE sends the BGP advertisement to a second CE, along with the transitive IGP attributes. Upon receiving the BGP advertisement, the second CE converts the BGP advertisement and transitive IGP attributes into corresponding IGP advertisements. The second CE may then propagate the IGP advertisements into its customer network as either internal VPN routes or as external routes accordingly.

Claims

1. A method for maintaining Interior Gateway Protocol (IGP) transparency of Virtual Private Network (VPN) routes when Border Gateway Protocol (BGP) is used as a Provider Edge Device (PE) to Customer Edge Device (CE) protocol in a computer network, the method comprising:

generating a BGP advertisement at a first CE to advertise one or more VPN routes of a customer network of the first CE, the BGP advertisement having one or more transitive IGP attributes for the advertised routes;

sending the BGP advertisement from the first CE to a first PE;

propagating the BGP advertisement from the first PE among devices of a provider network maintaining the transitive IGP attributes, one of the devices being a second PE;

sending the BGP advertisement from the second PE to a second CE, along with the transitive IGP attributes;

receiving the BGP advertisement at the second CE; and

in response, converting the BGP advertisement and transitive IGP attributes at the second CE into corresponding IGP advertisements.

2. The method as in claim 1, further comprising:

propagating the IGP advertisements from the second CE into a customer network of the second CE as either internal routes or as external routes based on the transitive IGP attributes.

3. The method as in claim 2, further comprising:

propagating the IGP advertisements as internal routes in response to the first and second CEs belonging to the same IGP domain, wherein the transitive IGP attributes indicate that the advertised routes are internal routes; and

propagating the IGP advertisements as external routes in response to one of either the first and second CEs belonging to different IGP domains, or in response to the first and second CEs belonging to the same IGP domain, wherein the transitive IGP attributes indicate that the advertised routes are external routes.

4. The method as in claim 3, further comprising:

determining whether the first and second CEs belong to the same IGP domain based on an IGP Domain Identifier (ID) transitive IGP attribute.

5. The method as in claim 1, further comprising:

configuring the transitive IGP attributes as one or more transitive IGP attributes selected from a group comprising;

an IGP Domain Identifier (ID) attribute;

an IGP Route Type attribute;

an IGP Router ID attribute; and

an IGP Metric attribute.

6. The method as in claim 1, further comprising:

carrying the transitive IGP attributes as one or more extended community attributes in the BGP advertisement.

7. The method as in claim 1, wherein the first and second CEs are in the same customer network and the second CE receives the BGP advertisement of VPN routes of the same customer network via the second PE, the method further comprising:

increasing an administrative distance of a BGP instance on the first CE within the BGP advertisement to persuade the second CE to select routes internal to the customer network rather than received routes from the BGP advertisement of the customer network.

8. The method as in claim 1, wherein the IGP is selected from a group comprising:

an Open Shortest Path First (OSPF) protocol;

an Intermediate-System-to-Intermediate-System (IS-IS) protocol;

a Routing Information Protocol (RIP); and

an Enhanced Interior Gateway Routing Protocol (EIGRP).

9. A system for maintaining Interior Gateway Protocol (IGP) transparency of Virtual Private Network (VPN) routes when Border Gateway Protocol (BGP) is used as a Provider Edge Device (PE) to Customer Edge Device (CE) protocol in a computer network, the system comprising:

a first CE configured to generate a BGP advertisement to advertise one or more VPN routes of a customer network of the first CE, the BGP advertisement having one or more transitive IGP attributes for the advertised routes;

a first PE configured to receive the BGP advertisement and to propagate the BGP advertisement into a provider network of the first PE maintaining the transitive IGP attributes;

a second PE configured to receive the BGP advertisement and to send the BGP advertisement along with the transitive IGP attributes; and

a second CE configured to receive the BGP advertisement from the second PE, the second CE further configured to convert the BGP advertisement and transitive IGP attributes into corresponding IGP advertisements.

10. The system as in claim 9, wherein the second CE is further configured to:

propagate the IGP advertisements into a customer network of the second CE as either internal routes or as external routes based on the transitive IGP attributes.

11. The system as in claim 10, wherein the second CE is further configured to:

propagate the IGP advertisements as internal routes in response to the first and second CEs belonging to the same IGP domain, wherein the transitive IGP attributes indicate that the advertised routes are internal routes; and

propagate the IGP advertisements as external routes in response to one of either the first and second CEs belonging to different IGP domains, or in response to the first and second CEs belonging to the same IGP domain, wherein the transitive IGP attributes indicate that the advertised routes are external routes.

12. An apparatus for maintaining Interior Gateway Protocol (IGP) transparency of Virtual Private Network (VPN) routes when Border Gateway Protocol (BGP) is used as a Provider Edge Device (PE) to Customer Edge Device (CE) protocol in a computer network, the apparatus comprising:

means for generating BGP advertisements to advertise one or more VPN routes of a customer network of the apparatus, the BGP advertisements having one or more transitive IGP attributes for the advertised routes;

means for sending BGP advertisements to PEs;

means for receiving BGP advertisements from PEs, the received BGP advertisements having one or more transitive IGP attributes corresponding to one or more VPN routes of a customer network of a remote apparatus; and

means for converting received BGP advertisements and transitive IGP attributes into corresponding IGP advertisements.

13. The apparatus as in claim 12, further comprising:

means for propagating the IGP advertisements into the customer network of the apparatus as either internal routes or as external routes based on the transitive IGP attributes.

14. The apparatus as in claim 13, further comprising:

means for propagating the IGP advertisements as internal routes in response to the first and second CEs belonging to the same IGP domain, wherein the transitive IGP attributes indicate that the advertised routes are internal routes; and

means for propagating the IGP advertisements as external routes in response to one of either the first and second CEs belonging to different IGP domains, or in response to the first and second CEs belonging to the same IGP domain, wherein the transitive IGP attributes indicate that the advertised routes are external routes.

15. A computer readable medium containing executable program instructions for maintaining Interior Gateway Protocol (IGP) transparency of Virtual Private Network (VPN) routes when Border Gateway Protocol (BGP) is used as a Provider Edge Device (PE) to Customer Edge Device (CE) protocol in a computer network, the computer readable medium adapted to operate on a device, the executable program instructions comprising program instructions for:

generating BGP advertisements to advertise one or more VPN routes of a customer network of the device, the BGP advertisements having one or more transitive IGP attributes for the advertised routes;

sending BGP advertisements to PEs;

receiving BGP advertisements from PEs, the received BGP advertisements having one or more transitive IGP attributes corresponding to one or more VPN routes of a customer network of a remote device; and

converting received BGP advertisements and transitive IGP attributes into corresponding IGP advertisements.

16. The computer readable medium as in claim 15, wherein the executable program instructions further comprise program instructions for:

propagating the IGP advertisements into the customer network of the device as either internal routes or as external routes based on the transitive IGP attributes.

17. The computer readable medium as in claim 16, wherein the executable program instructions further comprise program instructions for:

propagating the IGP advertisements as internal routes in response to the first and second CEs belonging to the same IGP domain, wherein the transitive IGP attributes indicate that the advertised routes are internal routes; and

propagating the IGP advertisements as external routes in response to one of either the first and second CEs belonging to different IGP domains, or in response to the first and second CEs belonging to the same IGP domain, wherein the transitive IGP attributes indicate that the advertised routes are external routes.

18. A Customer Edge Device (CE) for use with maintaining Interior Gateway Protocol (IGP) transparency of Virtual Private Network (VPN) routes when Border Gateway Protocol (BGP) is used as a Provider Edge Device (PE) to CE protocol in a computer network, the CE comprising:

one or more network interfaces configured send and receive BGP advertisements with one or more PEs;

a processor coupled to the one or more network interfaces and adapted to execute software processes; and

a memory adapted to store a routing process executable by the processor, the routing process configured to;

i) generate BGP advertisements to advertise one or more VPN routes of a customer network of the CE, the BGP advertisements having one or more transitive IGP attributes for the advertised routes, ii) send BGP advertisements to the one or more PEs, iii) receive BGP advertisements from the one or more PEs, the received BGP advertisements having one or more transitive IGP attributes corresponding to one or more VPN routes of a customer network of a remote CE, and iv) convert received BGP advertisements and transitive IGP attributes into corresponding IGP advertisements.

19. The CE as in claim 18, wherein the routing process is further configured to:

propagate the IGP advertisements into the customer network of the CE as either internal routes or as external routes based on the transitive IGP attributes.

20. The CE as in claim 19, wherein the routing process is further configured to:

propagate the IGP advertisements as internal routes in response to the first and second CEs belonging to the same IGP domain, wherein the transitive IGP attributes indicate that the advertised routes are internal routes; and

propagate the IGP advertisements as external routes in response to one of either the first and second CEs belonging to different IGP domains, or in response to the first and second CEs belonging to the same IGP domain, wherein the transitive IGP attributes indicate that the advertised routes are external routes.

21. A Provider Edge Device (PE) for use with maintaining Interior Gateway Protocol (IGP) transparency of Virtual Private Network (VPN) routes when Border Gateway Protocol (BGP) is used as a PE to Customer Edge Device (CE) protocol in a computer network, the PE comprising:

one or more network interfaces configured to receive incoming BGP advertisements from one or more CEs that advertise one or more VPN routes of a customer network of the CE, the received incoming BGP advertisements having one or more transitive IGP attributes for the advertised routes, the one or more network interfaces further configured to send outgoing BGP advertisements to one or more PEs;

a processor coupled to the one or more network interfaces and adapted to execute software processes; and

a memory adapted to store a routing process executable by the processor, the routing process configured to;

i) receive the incoming BGP advertisements, ii) generate outgoing BGP advertisements to advertise the advertised routes received from the one or more CEs, the outgoing BGP advertisements having the one or more transitive IGP attributes in addition to one or more corresponding non-transitive attributes, and iii) send the outgoing BGP advertisements to the one or more PEs.

22. The PE as in claim 21, wherein the at least one or more of the one or more PEs use an IGP as the PE-CE protocol, and at least one of the one or more PEs using an IGP as the PE-CE protocol is not configured to send the transitive IGP attributes to a second CE.

23. A Provider Edge Device (PE) for use with maintaining Interior Gateway Protocol (IGP) transparency of Virtual Private Network (VPN) routes when Border Gateway Protocol (BGP) is used as a PE to Customer Edge Device (CE) protocol in a computer network, the PE comprising:

one or more network interfaces configured to receive incoming BGP advertisements that advertise one or more VPN routes of a customer network of a CE, the received incoming BGP advertisements having one or more non-transitive IGP attributes for the advertised routes, the one or more network interfaces further configured to send outgoing BGP advertisements to one or more CEs;

a processor coupled to the one or more network interfaces and adapted to execute software processes; and

a memory adapted to store a routing process executable by the processor, the routing process configured to;

i) receive the incoming BGP advertisements, ii) generate outgoing BGP advertisements to advertise the advertised routes received from the one or more CEs, the outgoing BGP advertisements having one or more transitive IGP attributes translated from the non-transitive IGP attributes, and ii) send the BGP advertisements to the one or more CEs.

24. The PE as in claim 23, wherein the received incoming BGP advertisement was generated at an ingress PEs configured to use an IGP as the PE-CE protocol, and the ingress PEs using an IGP as the PE-CE protocol is not configured to generate a BGP advertisement having the transitive IGP attributes.