Dell SmartFabric OS10 User Guide Release 10.5.3

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

A maximum number of hops a BPDU travels before a receiving device discards it.

1. Change the forward-time parameter in CONFIGURATION mode, from 4 to 30, default 15.

   spanning-tree mst forward-time seconds

2. Change the hello-time parameter in CONFIGURATION mode, from 1 to 10, default 2. Dell Technologies 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, from 6 to 40, default 20.

   spanning-tree mst max-age seconds

4. Change the max-hops parameter in CONFIGURATION mode, from 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