# US 2014/0153567 A1 · System and Method for Implementation of Layer 2 Redundancy Protocols Across Multiple Networks > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2014/0153567 A1 - Document ID: US20140153567A1 - Status: Published application - Kind: A1 - Application number: 13/893,111 - Filed: 2013-05-13 - Published: 2014-06-05 - Earliest claimed: 2002-10-01 - Assignees: Foundry Networks, Inc. - Inventors: Andrew Tai-Chin Kuo; Gurudeep Kamat; Jordi Moncada-Elias; Ivy Pei-Shan Hsu; Rajkumar Jalan - Web page: https://patentgrep.com/patent/US20140153567A1 ## CPC - H04L 45/74: Address processing for routing - H04L 12/66: Arrangements for connecting between networks having differing types of switching systems, e.g. gateways - H04L: TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION (arrangements common to telegraphic and telephonic communication H04M) ## Abstract The system, method, and article of manufacture of the present invention allows multiple customers connected to a common external network to each implement a layer 2 redundancy protocol, such as the spanning tree protocol, in order to prevent layer 2 loops. Accordingly, a method is presented for providing an independent loop free layer 2 topology between a external network and a customer network comprising tagging control packets originating on the customer network with a unique identifier and tunneling the control packets received from the customer network between a plurality of boundary interface devices at the external network such that the control packets are routed back to the customer network based on the presence of the unique identifier in the control packet. The layer 2 redundancy protocol on the customer network converges based at least in part on the presence of control packets appearing on more than one port on the customer network. ## Claims ### Claim at position 1 1-17. (canceled) ### Claim 18 A method comprising: modifying, by a network device, a control packet to include: first information identifying a first network as a source of the control packet; and second information indicating that the control packet should be flooded through a second network distinct from the first network; and forwarding, by the network device, the modified control packet via one or more ports leading to the second network. ### Claim 19 (depends on 18) The method of claim 18 further comprising, subsequently to the forwarding: receiving the modified control packet; identifying the first information and the second information in the modified control packet; and reverting the modified control packet to its initial state prior to the modifying. ### Claim 20 (depends on 19) The method of claim 19 further comprising forwarding the reverted control packet via one or more ports leading to the first network. ### Claim 21 (depends on 18) The method of claim 18 wherein the modifying and forwarding are performed while the network device is in a preforwarding state, and wherein the network device does not forward any packets other than control packets from the first network while in the preforwarding state. ### Claim 22 (depends on 18) The method of claim 18 wherein modifying the control packet to include the first information comprises modifying fourth and fifth bytes of a MAC address of the control packet. ### Claim 23 (depends on 18) The method of claim 18 wherein modifying the control packet to include the second information comprises modifying a first byte of a MAC address of the control packet. ### Claim 24 (depends on 18) The method of claim 18 wherein the control packet implements Spanning Tree Protocol (STP) with respect to the first network. ### Claim 25 (depends on 24) The method of claim 24 wherein the control packet is a Bridge Protocol Data Unit (BPDU). ### Claim 26 (depends on 18) The method of claim 18 further comprising: modifying a second control packet to include: third information identifying a third network as a source of the control packet; and fourth information indicating that the control packet should be flooded through the second network; and forwarding, by the network device, the modified second control packet via the one or more ports leading to the second network. ### Claim 27 (depends on 26) The method of claim 26 further comprising: receiving the modified second control packet; identifying the third information and the fourth information in the modified second control packet; and reverting the modified second control packet to its initial state prior to the modifying. ### Claim 28 (depends on 27) The method of claim 27 further comprising forwarding the reverted second control packet via one or more ports leading to the third network. ### Claim 29 (depends on 26) The method of claim 26 wherein the second control packet is never forwarded to the first network. ### Claim 30 A network device comprising: a processor; a plurality of ports; and and a non-transitory storage medium having stored thereon program code that, when executed by the processor, causes the processor to: modify a control packet to include: first information identifying a first network as a source of the control packet; and second information indicating that the control packet should be flooded through a second network distinct from the first network; and forward the modified control packet via one or more ports in the plurality of ports leading to the second network. ### Claim 31 (depends on 30) The network device of claim 30 wherein the program code further causes the processor to, subsequently to the forwarding: receive the modified control packet; identify the first information and the second information in the modified control packet; and revert the modified control packet to its initial state prior to the modifying. ### Claim 32 (depends on 31) The network device of claim 31 wherein the program code further causes the processor to forward the reverted control packet via one or more ports leading to the first network. ### Claim 33 (depends on 30) The network device of claim 30 wherein the modifying and forwarding are performed while the network device is in a preforwarding state, and wherein the network device does not forward any packets other than control packets from the first network while in the preforwarding state. ### Claim 34 A non-transitory computer-readable storage medium having stored thereon program code that, when executed by a processor of a network device, causes the processor to: modify a control packet to include: first information identifying a first network as a source of the control packet; and second information indicating that the control packet should be flooded through a second network distinct from the first network; and forward the modified control packet via one or more ports leading to the second network. ### Claim 35 (depends on 34) The non-transitory computer-readable storage medium of claim 34 wherein the program code further causes the processor to, subsequently to the forwarding: receive the modified control packet; identify the first information and the second information in the modified control packet; and revert the modified control packet to its initial state prior to the modifying. ### Claim 36 (depends on 35) The non-transitory computer-readable storage medium of claim 35 wherein the program code further causes the processor to forward the reverted control packet via one or more ports leading to the first network. ### Claim 37 (depends on 34) The non-transitory computer-readable storage medium of claim 34 wherein the modifying and forwarding are performed while the network device is in a preforwarding state, and wherein the network device does not forward any packets other than control packets from the first network while in the preforwarding state.