OS10 Enterprise Edition User Guide Release 10.4.1.0

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Modify parameters

The root bridge sets the values for forward-delay, hello-time, max-age, and max-hops and overwrites the values set on other MST bridges.

Forward-time
Time an interface waits in the Discarding state and Learning state before it transitions to the Forwarding state.
Hello-time
Interval in which the bridge sends MST BPDUs.
Max-age
Length of time the bridge maintains configuration information before it refreshes that information by recomputing the MST topology.
Max-hops
Maximum number of hops a BPDU travels before a receiving device discards it.

Dell EMC recommends that only experienced network administrators change MST parameters. Poorly planned modification of the MST parameters can negatively affect network performance.

  1. Change the forward-time parameter in CONFIGURATION mode (4 to 30, default 15).
    spanning-tree mst forward-time 
                                           seconds
                                        
  2. Change the hello-time parameter in CONFIGURATION mode (1 to 10, default 2). Dell EMC recommends increasing the hello-time for large configurations (especially configurations with more ports).
    spanning-tree mst hello-time 
                                           seconds
                                        
  3. Change the max-age parameter in CONFIGURATION mode (6 to 40, default 20).
    spanning-tree mst max-age 
                                           seconds
                                        
  4. Change the max-hops parameter in CONFIGURATION mode (1 to 40, default 20).
    spanning-tree mst max-hops 
                                           number
                                        

MST configuration

OS10(config)# spanning-tree mst
                                 OS10(config)# spanning-tree mst forward-time 16
                                 OS10(config)# spanning-tree mst hello-time 5
                                 OS10(config)# spanning-tree mst max-age 10
                                 OS10(config)# spanning-tree mst max-hops 30
                              

View MSTP parameter values

OS10# show spanning-tree active
                                 Spanning tree enabled protocol msti with force-version mst
                                 MSTI 0 VLANs mapped 1,31-4093
                                 Executing IEEE compatible Spanning Tree Protocol
                                 Root ID    Priority 32768, Address 3417.4455.667f
                                 Root Bridge hello time 2, max age 20, forward delay 15, max hops 20
                                 Bridge ID    Priority 32768, Address 90b1.1cf4.a523
                                 Configured hello time 10, max age 40, forward delay 30, max hops 40
                                 CIST regional root ID Priority 32768, Address 90b1.1cf4.a523
                                 CIST external path cost 500
                                 Interface                                                 Designated
                                 Name           PortID   Prio  Cost Sts   Cost Bridge ID          PortID
                                 -----------------------------------------------------------------------------
                                 ethernet1/1/5  128.276  128   500  FWD   0    32768    3417.4455.667f  128.146
                                 ethernet1/1/6  128.280  128   500  BLK   0    32768    3417.4455.667f  128.150
                                 Interface
                                 Name            Role  PortID   Prio  Cost  Sts  Cost  Link-type Edge
                                 ------------------------------------------------------------------
                                 ethernet1/1/5   Root  128.276  128   500   FWD  0     AUTO      No
                                 ethernet1/1/6   Altr  128.280  128   500   BLK  0     AUTO      No
                              

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