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Dell EMC SmartFabric OS10 User Guide Release 10.5.0

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Global parameters

The root bridge sets the values for forward-time, hello-time, and max-age, and overwrites the values set on other bridges participating in the RSTP group.

NOTE Dell EMC recommends that only experienced network administrators change the RSTP group parameters. Poorly planned modification of the RSTP parameters can negatively affect network performance.
Forward-time
15 seconds — Amount of time an interface waits in the Learning state before it transitions to the Forwarding state.
Hello-time
2 seconds — Time interval in which the bridge sends RSTP BPDUs.
Max-age
20 seconds — Length of time the bridge maintains configuration information before it refreshes that information by recomputing the RSTP topology.
Port cost
Port cost values to set the path cost of the interface:
  • 100-Mb/s Ethernet interfaces — 200000
  • 1-Gigabit Ethernet interfaces — 20000
  • 10-Gigabit Ethernet interfaces — 2000
  • 40-Gigabit Ethernet interfaces — 500
  • Port-channel with 100 Mb/s Ethernet interfaces — 200000
  • Port-channel with 1-Gigabit Ethernet interfaces — 20000
  • Port-channel with 10-Gigabit Ethernet interfaces — 2000
  • Port-channel with 1x40Gigabit Ethernet interface — 500
  • Port-channel with 2x40Gigabit Ethernet interfaces — 250
  • Change the forward-time in CONFIGURATION mode, from 4 to 30, default 15. 
    spanning-tree rstp forward-time seconds
  • Change the hello-time in CONFIGURATION mode, from 1 to 10, default 2. With large configurations, especially those configurations with more ports, Dell EMC recommends increasing the hello-time. 
    spanning-tree rstp hello-time seconds
  • Change the max-age in CONFIGURATION mode, from 6 to 40, default 20. 
    spanning-tree rstp max-age seconds

View current global parameter values 

OS10# show spanning-tree active 
 
Spanning tree enabled protocol rstp with force-version rstp
Executing IEEE compatible Spanning Tree Protocol
Root ID    Priority 32768, Address 90b1.1cf4.9b8a
Root Bridge hello time 2, max age 20, forward delay 15
Bridge ID    Priority 32768, Address 90b1.1cf4.9b8a
We are the root
Configured hello time 2, max age 20, forward delay 15
Interface                                       Designated
Name          PortID  Prio Cost Sts Cost Bridge ID  PortID
------------------------------------------------------------------- 
ethernet1/1/1 244.128 128  500  BLK 0    32768 90b1.1cf4.9b8a  128.244
ethernet1/1/2 248.128 128  500  BLK 0    32768 90b1.1cf4.9b8a  128.248
ethernet1/1/3 252.128 128  500  FWD 0    32768 90b1.1cf4.9b8a  128.252
ethernet1/1/4 256.128 128  500  BLK 0    32768 90b1.1cf4.9b8a  128.256
Interface
Name          Role PortID  Prio Cost Sts Cost Link-type Edge
---------------------------------------------------------- 
ethernet1/1/1 Altr 128.244 128  500  BLK 0    AUTO      No
ethernet1/1/2 Altr 128.248 128  500  BLK 0    AUTO      No
ethernet1/1/3 Root 128.252 128  500  FWD 0    AUTO      No
ethernet1/1/4 Altr 128.256 128  500  BLK 0    AUTO      No

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