Rapid Spanning Tree Protocol (RSTP) | 779Figure 38-8. bridge-priority Command ExampleSNMP Traps for Root Elections and Topology ChangesEnable SNMP traps for RSTP, MSTP, and PVST+ collectively using the command snmp-server enabletraps xstp.Fast Hellos for Link State DetectionFast Hellos for Link State Detection is available only on platform: s zUse RSTP Fast Hellos to achieve sub-second link-down detection so that convergence is triggered faster.The standard RSTP link-state detection mechanism does not offer the same low link-state detection speed.RSTP Fast Hellos decrease the hello interval to the order of milliseconds and all timers derived from thehello timer are adjusted accordingly. This feature does not inter-operate with other vendors, and isavailable only for RSTP.Task Command Syntax Command ModeConfigure a hello time on the order of milliseconds. hello-time milli-second intervalRange: 50 - 950 millisecondsPROTOCOL RSTPFTOS(conf-rstp)#do show spanning-tree rstp briefExecuting IEEE compatible Spanning Tree ProtocolRoot ID Priority 0, Address 0001.e811.2233Root Bridge hello time 50 ms, max age 20, forward delay 15Bridge ID Priority 0, Address 0001.e811.2233We are the rootConfigured hello time 50 ms, max age 20, forward delay 15Note: The hello time is encoded in BPDUs in increments of 1/256ths of a second. The standard minimumhello time in seconds is 1 second, which is encoded as 256. Millisecond hello times are encoded usingvalues less than 256; the millisecond hello time equals (x/1000)*256.Note: When millisecond hellos are configured, the default hello interval of 2 seconds is still used for edgeports; the millisecond hello interval is not used.FTOS(conf-rstp)#bridge-priority 409604:27:59: %RPM0-P:RP2 %SPANMGR-5-STP_ROOT_CHANGE: RSTP root changed. My Bridge ID:4096:0001.e80b.88bd Old Root: 32768:0001.e801.cbb4 New Root: 4096:0001.e80b.88bdNew root bridge IDOld root bridge ID
