Users Guide

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 A maximum number of hops a BPDU travels before a receiving device discards it.
NOTE: Dell EMC recommends that only experienced network administrators change MST parameters. Poorly planned
modification of MST parameters can negatively affect network performance.
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 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, 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
Interface parameters
Adjust two interface parameters to increase or decrease the likelihood that a port becomes a forwarding port.
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Layer 2