Patent ID: 7660271

Claim:
A method comprising: in a first network device operably connected via a trunk link to a second and a third network device, wherein the first, second and third network devices are operative to implement a plurality of virtual LANs (VLANs) including a common spanning tree protocol instance and a plurality of per-VLAN spanning tree protocol instances; wherein the common spanning tree protocol instance is implemented across respective native VLANs on the first, second and third network devices, wherein the first network device supports a configurable native VLAN, and wherein the configurable native VLAN is configured to a first native VLAN, wherein the second network device includes a second native VLAN, wherein the third network device includes the second native VLAN, and wherein the second native VLAN is different from the first native VLAN: receiving, at the first network device, a bridge protocol data unit (BPDU) transmitted from the second network device; if the received BPDU is a common spanning tree BPDU: removing a VLAN identifier from the common spanning tree BPDU, if the common spanning tree BPDU includes a VLAN identifier, prior to processing thereof and conditionally adding a VLAN identifier corresponding to the second native VLAN, prior to transmitting the common spanning tree BPDU to the third network device, based on whether the third network device supports a configurable native VLAN or a fixed native VLAN, the conditionally adding comprising: if the second native VLAN included in the third network device is a fixed native VLAN, adding, prior to transmitting the common spanning tree BPDU to the third network device, a VLAN identifier corresponding to the second native VLAN.