H3C Technologies H3C WX3000 Series Unified Switches - Manual (Page 190)

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STP-compatible mode, where the ports of a device send STP BPDUs to neighboring devices. If
STP-enabled devices exist in a switched network, you can use the stp mode stp command to
configure an MSTP-enabled device to operate in STP-compatible mode.
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RSTP-compatible mode, where the ports of a device send RSTP BPDUs to neighboring devices. If
RSTP-enabled devices exist in a switched network, you can use the stp mode rstp command to
configure an MSTP-enabled device to operate in RSTP-compatible mode.
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MSTP mode, where the ports of a device send MSTP BPDUs or STP BPDUs (if the device is
connected to STP-enabled devices) to neighboring devices. In this case, the device is
MSTP-capable.
Configuration procedure
Follow these steps to configure the MSTP operation mode:
To do… Use the command… Remarks
Enter system view system-view —
Configure the MSTP operation
mode
stp mode { stp | rstp | mstp }
Required
An MSTP-enabled device operates
in the MSTP mode by default.
Configuration example
# Specify the MSTP operation mode as STP-compatible.
<device> system-view
[device] stp mode stp
Configuring the Maximum Hop Count of an MST Region
The maximum hop count configured on the region root is also the maximum hops of the MST region.
The value of the maximum hop count limits the size of the MST region.
A configuration BPDU contains a field that maintains the remaining hops of the configuration BPDU.
And the device discards the configuration BPDUs whose remaining hops are 0. After a configuration
BPDU reaches a root bridge of a spanning tree in an MST region, the value of the remaining hops field
in the configuration BPDU is decreased by 1 every time the configuration BPDU passes one device.
Such a mechanism disables the devices that are beyond the maximum hop count from participating in
spanning tree calculation, and thus limits the size of an MST region.
With such a mechanism, the maximum hop count configured on the device operating as the root bridge
of the CIST or an MSTI in an MST region becomes the network diameter of the spanning tree, which
limits the size of the spanning tree in the current MST region. The devices that are not root bridges in the
MST region adopt the maximum hop settings of their root bridges.
Configuration procedure
Follow these steps to configure the maximum hop count for an MST region:
To do… Use the command… Remarks
Enter system view system-view —
Configure the maximum hop count
of the MST region
stp max-hops hops
Required
By default, the maximum hop count
of an MST region is 20.