Reference Guide

Port cost Value that is based on the interface type. The previous table lists the default values. The greater the port cost, the
less likely the port is selected to be a forwarding port.
Port priority Inuences the likelihood that a port is selected to be a forwarding port in case that several ports have the same
port cost.
• Change the port cost of an interface in INTERFACE mode (1 to 200000000).
spanning-tree rstp cost cost
• Change the port priority of an interface in INTERFACE mode (0 to 240, default 128).
spanning-tree rstp priority priority-value
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
-------------------------------------------------------------------
ethernet3/1/1 244.128 128 500 BLK 0 32768 90b1.1cf4.9b8a 128.244
ethernet3/1/2 248.128 128 500 BLK 0 32768 90b1.1cf4.9b8a 128.248
ethernet3/1/3 252.128 128 500 FWD 0 32768 90b1.1cf4.9b8a 128.252
ethernet3/1/4 256.128 128 500 BLK 0 32768 90b1.1cf4.9b8a 128.256
Interface
Name Role PortID Prio Cost Sts Cost Link-type Edge
----------------------------------------------------------
ethernet3/1/1 Altr 128.244 128 500 BLK 0 AUTO No
ethernet3/1/2 Altr 128.248 128 500 BLK 0 AUTO No
ethernet3/1/3 Root 128.252 128 500 FWD 0 AUTO No
ethernet3/1/4 Altr 128.256 128 500 BLK 0 AUTO No
Root bridge selection
RSTP determines the root bridge. Assign one bridge a lower priority to increase the likelihood that it is selected as the root bridge.
• Assign a number as the bridge priority or designate it as the primary or secondary root in CONFIGURATION mode. Congure the
priority value range (0 to 65535 in multiples of 4096, default 32768). The lower the number assigned, the more likely this bridge
becomes the root bridge.
spanning-tree rstp priority priority-value
View bridge priority and root bridge assignment
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 3417.4455.667f
Root Bridge hello time 2, max age 20, forward delay 15
Bridge ID Priority 36864, Address 90b1.1cf4.a523
Configured hello time 2, max age 20, forward delay 15
Interface Designated
Name PortID Prio Cost Sts Cost Bridge ID PortID
----------------------------------------------------------------------
ethernet1/1/6:3 128.282 128 2000 FWD 0 32768 3417.4455.667f 128.152
ethernet1/1/6:4 128.283 128 2000 BLK 0 32768 3417.4455.667f 128.153
Interface
Name Role PortID Prio Cost Sts Cost Link-type Edge
-----------------------------------------------------------------
Layer 2
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