This command enables tracing of spanning tree BPDUs received by the switch. Spanning tree should be enabled on the device and on the interface in order to monitor packets for a particular interface.
| Default | Disabled |
| Format | debug spanning-tree bpdu receive |
| Mode | Privileged EXEC |
A sample output of the trace message is shown below.
<15> JAN 01 01:02:04 192.168.17.29-1 DOT1S[191096896]: dot1s_debug.c(1249) 101 % Pkt RX - Intf: 1/0/9(9), Source_Mac: 00:11:88:4e:c2:10 Version: 3, Root Mac: 00:11:88:4e:c2:00, Root Priority: 0x8000 Path Cost: 0
The following parameters are displayed in the trace message:
| Parameter | Definition |
|---|---|
| RX | A packet received by the device. |
| Intf | The interface that the packet came in on. Format used is unit/port/slot (internal interface number). Unit is always shown as 1 for interfaces on a non-stacking device. |
| Source_Mac | Source MAC address of the packet. |
| Version | Spanning tree protocol version (0-3). 0 refers to STP, 2 RSTP and 3 MSTP. |
| Root_Mac | MAC address of the CIST root bridge. |
| Root_Priority | Priority of the CIST root bridge. The value is between 0 and 61440. It is displayed in hex in multiples of 4096. |
| Path_Cost | External root path cost component of the BPDU. |
