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06-01-2017 12:00 AM - edited 06-01-2017 12:48 AM
06-01-2017 12:00 AM - edited 06-01-2017 12:48 AM
Spanning tree Which switch is root?
Hi, I have 2 switches that claim to be root on spanning tree. THe switches are linked on a 1gbps fiber with gbics. Why are both switches showing as root?
The config on the core is
spanning-tree
no spanning-tree bpdu-throttle
spanning-tree root primary priority 0 force-version rstp-operation
The config on the link switch
spanning-tree root secondary priority 1 force-version rstp-operation
See below for info from "sh span" for both
My core
Multiple Spanning Tree (MST) Information
STP Enabled : Yes
Force Version : RSTP-operation
IST Mapped VLANs : 1-4094
Switch MAC Address : 2c59e5-25c700
Switch Priority : 0
Max Age : 20
Max Hops : 20
Forward Delay : 15
Topology Change Count : 620,526
Time Since Last Change : 12 mins
CST Root MAC Address : 2c59e5-25c700
CST Root Priority : 0
CST Root Path Cost : 0
CST Root Port : This switch is root
IST Regional Root MAC Address : 2c59e5-25c700
IST Regional Root Priority : 0
IST Regional Root Path Cost : 0
IST Remaining Hops : 20
Root Guard Ports :
Loop Guard Ports :
TCN Guard Ports :
BPDU Protected Ports :
BPDU Filtered Ports :
PVST Protected Ports :
PVST Filtered Ports :
Root Inconsistent Ports :
Loop Inconsistent Ports :
And my link switch at my main high site for our WAN
Multiple Spanning Tree (MST) Information
STP Enabled : Yes
Force Version : RSTP-operation
IST Mapped VLANs : 1-4094
Switch MAC Address : d89d67-85af00
Switch Priority : 4096
Max Age : 20
Max Hops : 20
Forward Delay : 15
Topology Change Count : 0
Time Since Last Change : 128 days
CST Root MAC Address : d89d67-85af00
CST Root Priority : 4096
CST Root Path Cost : 0
CST Root Port : This switch is root
IST Regional Root MAC Address : d89d67-85af00
IST Regional Root Priority : 4096
IST Regional Root Path Cost : 0
IST Remaining Hops : 20
Root Guard Ports :
Loop Guard Ports :
TCN Guard Ports :
BPDU Protected Ports :
BPDU Filtered Ports : 1-24
PVST Protected Ports :
PVST Filtered Ports : 6
Root Inconsistent Ports :
Loop Inconsistent Ports :
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06-02-2017 07:18 AM
06-02-2017 07:18 AM
Re: Spanning tree Which switch is root?
Check:
-mst settings on both switches. Only if they match, it'll be a single mst area
-the status of link between switches. Also run show commands for stp on those ports.
afaik, it's best to have vlan1 present untagged on this link
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