3Com 4510G - Enabling the Output of Port State Transition Information

4-28
z dot1s: 802.1s-compliant standard format, and
z legacy: Compatible format
By default, the packet format recognition mode of a port is auto, namely the port automatically
distinguishes the two MSTP packet formats, and determines the format of packets it will send based on
the recognized format. You can configure the MSTP packet format on a port. After the configuration,
when working in MSTP mode, 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.
Make this configuration on the root bridge and on the leaf nodes separately.
Follow these steps to configure the MSTP packet format to be supported on a port or a group of ports:
To do... Use the command... Remarks
Enter system view system-view —
Enter Ethernet
interface view, or
Layer 2
aggregate
interface view
interface interface-type
interface-number
Enter
interface
view or
port group
view
Enter port group
view
port-group manual
port-group-name
Required
Use either command.
Configure the mode the port
uses to recognize/send MSTP
packets
stp compliance { auto | dot1s |
legacy }
Required
auto by default
z MSTP provides the MSTP packet format incompatibility guard function. 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.
z MSTP provides the MSTP packet format frequent change guard function. If a port receives MSTP
packets of different formats frequently, this means that the MSTP packet format configuration
contains errors. In this case, if the port is working in MSTP mode, it will be disabled for protection.
Those ports closed thereby can be restored only by the network administrators.
Enabling the Output of Port State Transition Information
In a large-scale, MSTP-enabled network, there are a large number of MSTIs, so ports may frequently
transition from one state to another. In this situation, you can enable devices to output the port state
transition information of all MSTIs or the specified MSTI so as to monitor the port states in real time.
Make this configuration on the root bridge and on the leaf nodes separately.
Follow these steps to enable output of port state transition information:
To do... Use the command... Remarks
Enter system view system-view —