Operation Manual – MSTPH3C S3100 Series Ethernet Switches Chapter 1 MSTP Configuration1-261.3.6 Configuring the MSTP Operation ModeTo make a MSTP-enabled switch compatible with STP/RSTP, MSTP provides thefollowing three operation modes:z STP-compatible mode, where the ports of a switch send STP BPDUs toneighboring devices. If STP-enabled switches exist in a switched network, you canuse the stp mode stp command to configure an MSTP-enabled switch to operatein STP-compatible mode.z RSTP-compatible mode, where the ports of a switch send RSTP BPDUs toneighboring devices. If RSTP-enabled switches exist in a switched network, youcan use the stp mode rstp command to configure an MSTP-enabled switch tooperate in RSTP-compatible mode.z MSTP mode, where the ports of a switch send MSTP BPDUs or STP BPDUs (ifthe switch is connected to STP-enabled switches) to neighboring devices. In thiscase, the switch is MSTP-capable.I. Configuration procedureTable 1-14 Configure the MSTP operation modeOperation Command DescriptionEnter system view system-view —Configure the MSTPoperation modestp mode { stp | rstp |mstp }RequiredAn MSTP-enabled switchoperates in the MSTPmode by default.II. Configuration example# Specify the MSTP operation mode as STP-compatible. system-view[Sysname] stp mode stp1.3.7 Configuring the Maximum Hop Count of an MST RegionThe maximum hop count configured on the region root is also the maximum hops of theMST 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 theconfiguration BPDU. And a switch discards the configuration BPDUs whose remaininghops are 0. After a configuration BPDU reaches a root bridge of a spanning tree in anMST region, the value of the remaining hops field in the configuration BPDU isdecreased by 1 every time the configuration BPDU passes one switch. Such a
