1-21Configuration example# Configure GigabitEthernet 1/0/1 to recognize and send packets in dot1s format. system-view[Sysname] interface GigabitEthernet 1/0/1[Sysname-GigabitEthernet1/0/1] stp compliance dot1s# Restore the default mode for GigabitEthernet 1/0/1 to recognize/send MSTP packets.[Sysname-GigabitEthernet1/0/1] undo stp complianceConfiguring the MSTP Operation ModeTo make an MSTP-enabled switch compatible with STP/RSTP, MSTP provides the following threeoperation modes:z STP-compatible mode, where the ports of a switch send STP BPDUs to neighboring devices. IfSTP-enabled switches exist in a switched network, you can use the stp mode stp command toconfigure an MSTP-enabled switch to operate in STP-compatible mode.z RSTP-compatible mode, where the ports of a switch send RSTP BPDUs to neighboring devices. IfRSTP-enabled switches exist in a switched network, you can use the stp mode rstp command toconfigure an MSTP-enabled switch to operate in RSTP-compatible mode.z MSTP mode, where the ports of a switch send MSTP BPDUs or STP BPDUs (if the switch isconnected to STP-enabled switches) to neighboring devices. In this case, the switch isMSTP-capable.Configuration procedureFollow these steps to configure the MSTP operation mode:To do... Use the command... RemarksEnter system view system-view —Configure the MSTP operationmode stp mode { stp | rstp | mstp }RequiredAn MSTP-enabled switch operatesin the MSTP mode by default.Configuration example# Specify the MSTP operation mode as STP-compatible. system-view[Sysname] stp mode stpConfiguring the Maximum Hop Count of an MST RegionThe 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 a switch discards the configuration BPDUs whose remaining hops are 0. After a configurationBPDU reaches a root bridge of a spanning tree in an MST region, the value of the remaining hops fieldin 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 hop count from participating inspanning tree calculation, and thus limits the size of an MST region.
