H3C Technologies H3C S12500 Series Switches - Manual (Page 97)

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You can configure the MSTP packet format on a port. When operating in MSTP mode after the
configuration, the port sends and receives only MSTP packets of the format you have configured to
communicate with devices that send packets of the same format.
MSTP provides MSTP packet format incompatibility guard. In MSTP mode, if a port is configured to
recognize/send MSTP packets in a mode other than auto, and receives a packet in a format different
from the specified type, the port will become a designated port and remain in the discarding state to
prevent the occurrence of a loop.
MSTP provides MSTP packet format frequent change guard. If a port receives MSTP packets of different
formats frequently, the MSTP packet format configuration contains errors. If the port is operating in MSTP
mode, it will be shut down for protection. Ports disabled in this way can be re-activated after a detection
interval. For more information about the detection interval, see Fundamentals Configuration Guide.
To configure the MSTP packet format to be supported on a port or a group of ports:
Step Command Remarks
1. Enter system view. system-view N/A
2. Enter interface view or port group
view.
• Enter Ethernet interface
view or Layer 2 aggregate
interface view:
interface interface-type
interface-number
• Enter port group view:
port-group manual
port-group-name
Use either command.
3. Configure the mode the port uses to
recognize/send MSTP packets. stp compliance { auto | dot1s |
legacy }
The default setting is auto.
Enabling the spanning tree feature
CAUTION:
You can disable the spanning tree feature for certain ports with the undo stp enable command to exclude
them from spanning tree calculation and save CPU resources of the switch. However, use this command
with caution because the ports with the spanning tree feature disabled will keep forwarding data traffic
and discard STP BPDUs, and loops can occur.
You must enable the spanning tree feature for the switch before any other spanning tree related
configurations can take effect.
Enabling the spanning tree protocol in STP, RSTP, or MSTP
mode
In STP/RSTP/MSTP mode, make sure the spanning tree feature is enabled globally and on the desired
ports.
To enable the spanning tree protocol in STP, RSTP, or MSTP mode: