Operation Manual – MSTP
H3C S3100-52P Ethernet Switch
Chapter 1 MSTP Configuration
1-24
Caution:
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Once you specify a switch as the root bridge or a secondary root bridge by using the
stp root primary
or
stp root secondary
command, the bridge priority of the switch
cannot be configured any more.
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During the selection of the root bridge, if multiple switches have the same bridge
priority, the one with the smallest MAC address becomes the root bridge.
II. Configuration example
# Set the bridge priority of the current switch to 4,096 in MSTI 1.
<Sysname> system-view
[Sysname] stp instance 1 priority 4096
1.3.5 Configuring How a Port Recognizes and Sends MSTP Packets
A port can be configured to recognize and send MSTP packets in the following modes.
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Automatic mode. Ports in this mode determine the format of the MSTP packets to
be sent according to the format of the received packets.
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Legacy mode. Ports in this mode recognize/send packets in legacy format.
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802.1s mode. Ports in this mode recognize/send packets in dot1s format.
A port acts as follows according to the format of MSTP packets forwarded by a peer
switch or router.
When a port operates in the automatic mode:
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The port automatically determines the format (legacy or dot1s) of received MSTP
packets and then determines the format of the packets to be sent accordingly, thus
communicating with the peer devices.
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If the format of the received packets changes repeatedly, MSTP will shut down the
corresponding port to prevent network storm. A port shut down in this way can only
be brought up by the network administrator.
When a port operates in the legacy mode:
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The port recognizes and sends MSTP packets in legacy format. In this case, the
port can only communicate with the peer through packets in legacy format.
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If packets in dot1s format are received, the port turns to discarding state to prevent
network storm.
When a port operates in the 802.1s mode:
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The port recognizes and sends MSTP packets in dot1s format. In this case, the
port can only communicate with the peer through packets in dot1s format.
