Stp Mcheck - H3C s3600 series Command Manual

The maximum hop count configured on the region roots of an MST region limits the size of the MST
region.
A configuration BPDU contains a field that maintains the remaining hops of the configuration BPDU.
And a switch discards the configuration BPDUs whose remaining hops are 0. After a configuration
BPDU reaches a root bridge of a spanning tree in a MST region, the value of the remaining hops field in
the configuration BPDU is decreased by 1 every time the configuration BPDU passes one switch. Such
a mechanism disables the switches that are beyond the maximum hops from participating in spanning
tree calculation, and thus limits the size of an MST region.
With such a mechanism, the maximum hops configured on the switch operating as the root bridge of the
CIST or an MSTI in a MST region becomes the network diameter of the spanning tree, which limits the
size of the spanning tree in the current MST region. The switches that are not root bridges in an MST
region adopt the maximum hop settings of the root bridge.
Examples
# Set the maximum hop count of the current MST region to 35.
<Sysname> system-view
System View: return to User View with Ctrl+Z.
[Sysname] stp max-hops 35

stp mcheck

Syntax
stp mcheck
View
System view, Ethernet port view
Parameters
None
Description
Use the stp mcheck command to perform the mCheck operation on the current port.
When a port on an MSTP-enabled upstream switch connects with an STP-enabled downstream switch,
the port operates in the STP-compatible mode automatically. But when the STP-enabled downstream
switch is then replaced by an MSTP-enabled switch, the port cannot automatically transit to the MSTP
mode but still remains in the STP-compatible mode. In this case, you can force the port to transit to the
MSTP mode by performing the mCheck operation on the port.
Similarly, when a port on an RSTP-enabled upstream switch connects with an STP-enabled
downstream switch, the port operates in the STP-compatible mode. But when the STP-enabled
downstream switch is then replaced by an MSTP-enabled switch, the port cannot automatically transit
to the MSTP mode but remains in the STP-compatible mode. In this case, you can force the port to
transit to the MSTP-compatible mode by performing the mCheck operation on the port.
Related commands: stp mode, stp interface mcheck.
Examples
# Perform the mCheck operation on Ethernet 1/0/1.
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