Stp Mcheck - 3Com 8807 Command Reference Manual

MSTP Configuration Commands 195
Use the undo stp max-hops command to restore the default Max Hops.
On CIST and MSTIs, the Max Hops configured on the region root determines the
max switching network diameter supported by the local MST region. As the BPDU
travels from the spanning tree root, each time when it is forwarded by a switch,
the max hops will be reduced by 1. The switch discards the configuration BPDU
with 0 hops left, thereby limiting the network scale inside the region. If the current
switch is a CIST root bridge or MSTI root bridge in an MST region, the Max Hops
configured on it will be the network diameter of the spanning tree to limit its scale
in the local MST region. The Max Hops configured on the root bridge in an MST
region will be adopted by other switches in the same region.
Example
# Set the Max Hops of an MST region to 35.
<SW8800>system-view
System View: return to User View with Ctrl+Z.
[SW8800] stp max-hops 35

stp mcheck

Syntax
stp mcheck
View
Ethernet port view
Parameter
None
Description
Use the stp mcheck command to perform mCheck on the current port.
If a port of an MSTP switch on a switching network has ever been connected to an
STP switch, the port will automatically transit to operate in STP-compatible mode.
However, when the STP switch is removed, the port stays in STP-compatible mode
and cannot automatically transit back to MSTP mode. In this case, you can
perform mCheck operation to transit the port to MSTP mode by force.
n
By default, MSTP runs in MSTP mode, which is compatible with RSTP and STP (This
mode can recognize MSTP BPDU, STP config BPDU and RSTP config BPDU).
However, the STP switch can only recognize config BPDU (STP BPDU) sent by the
STP and RSTP bridges. After the switch running STP-compatible mode switches
back to MSTP mode, it will not send MSTP BPDU if you do not execute the stp
mcheck command. Therefore, the connected device still sends config BPDU (STP
BPDU) to it, causing the same configuration exist in different regions and other
problems. Remember to perform stp interface mCheck after modifying stp mode.
Related command: stp mode, stp interface mcheck.
Example
# Set mcheck parameter for Ethernet2/1/1.
<SW8800>system-view
System View: return to User View with Ctrl+Z.