Huawei completed the following steps to diagnose the problem:2. Queried traffic statistics and debug information on the switches. The BPDU packets from NE40Es were discarded. The RSTP topology on the NE40Es was not stable and all ports received/transmitted BPDU packets.
1. Captured packets. The BPDU packets sent by the switches carried VLAN tags. (Do not perform this check on a PC running the Windows OS, which automatically deletes VLAN tags from packets.)
3. Checked for the specific STP type used on the switches. Although RSTP was enabled on the configuration interface, the effective STP on the switches was Cisco's proprietary Per-VLAN Spanning Tree (PVST).
4. Checked the differences between RSTP implementation and PVST implementation. On PVST-enabled switches, a separate protocol packet is sent and a spanning tree instance is maintained for each VLAN. RSTP-enabled NE40Es do not support multiple VLANs, and therefore cannot send protocol packets or maintain spanning tree instances on a per-VLAN basis.
5. Enabled PVST globally and configured multi-process RSTP on the NE40Es. One root bridge was elected.