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New Member

finding root switch

Hi all, how do I find this on my network ? when I do sh spanning tree, it says root id, and bridge id, what is what here ?

2 REPLIES

Re: finding root switch

Hi Carl,

When you do the " Show spanning-tree detail" on the switch, it will show the root swithc ID and its priority.

Once you do the " show spanning-tree detail" on the root switch, this will show you the same mac-address on the switch. There is not other method which will automatically tell you that which switch is the root switch. You have to do this manually on each switch. That's why when we set up the network for the first time, we define that which switch will be primary root switch adn which one will be the secondry root switch on the network. This will give us a total view of the L2 network topology.

Switch# show spanning-tree detail

VLAN0001 is executing the ieee compatible Spanning Tree protocol

Bridge Identifier has priority 49152, sysid 1, address 0003.fd63.9580

Configured hello time 2, max age 20, forward delay 15

Current root has priority 32768, address 0001.42e2.cdd0

Root port is 24 (GigabitEthernet0/1), cost of root path is 3038

Topology change flag not set, detected flag not set

Number of topology changes 0 last change occurred 1d16h ago

Times: hold 1, topology change 35, notification 2

hello 2, max age 20, forward delay 15

Timers: hello 0, topology change 0, notification 0, aging 300

Uplinkfast enabled

Port 1 (GigabitEthernet0/1) of VLAN0001 is forwarding

Port path cost 3019, Port priority 128, Port Identifier 128.24.

Designated root has priority 32768, address 0001.42e2.cdd0

Designated bridge has priority 32768, address 00d0.bbf5.c680

Designated port id is 128.25, designated path cost 19

Timers: message age 2, forward delay 0, hold 0

Number of transitions to forwarding state: 1

Link type is point-to-point by default

BPDU: sent 0, received 72364

HTH,Please rate if it does.

-amit singh

New Member

Re: finding root switch

for example

sh spann-tree

VLAN0024

Spanning tree enabled protocol ieee

Root ID Priority 32792

Address 000e.84da.3200

Cost 8

Port 1 (GigabitEthernet0/1)

Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec

Bridge ID Priority 32792 (priority 32768 sys-id-ext 24)

Address 0019.2f36.9880

Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec

Aging Time 300

port Gi0/1 go to root brigde direction.

look at switch that connected to Gi0/1 of above mantioned switch, and repeat operation till you get root bridge

Spanning tree enabled protocol ieee

Root ID Priority 32792

Address 000e.84da.3200

This bridge is the root

Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec

Bridge ID Priority 32792 (priority 32768 sys-id-ext 24)

Address 000e.84da.3200

Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec

Aging Time 300

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