Change Root Bridge

[dacruzer1]

Hello Everyone,

Can someone tell me how to move a VLAN from one switch to another:

This is where the root bridge (CISCO 3550) is currently at:

WM-2ndFloor-PrintSwitch#sh spanning-tree vlan 64

VLAN0064
  Spanning tree enabled protocol ieee
  Root ID    Priority    32832
             Address     0013.8009.1f80
             This bridge is the root
             Hello Time   2 sec  Max Age 20 sec  Forward Delay 15 sec

  Bridge ID  Priority    32832  (priority 32768 sys-id-ext 64)
             Address     0013.8009.1f80
             Hello Time   2 sec  Max Age 20 sec  Forward Delay 15 sec
             Aging Time 300

Interface           Role Sts Cost      Prio.Nbr Type
------------------- ---- --- --------- -------- --------------------------------
Fa0/1               Desg FWD 19        128.1    P2p

I would like to move it to this switch: (3750X)

WM-Switch01-3750X#sh spanning-tree vlan 64

VLAN0064
  Spanning tree enabled protocol ieee
  Root ID    Priority    32832
             Address     0013.8009.1f80
             Cost        23
             Port        80 (GigabitEthernet2/1/2)
             Hello Time   2 sec  Max Age 20 sec  Forward Delay 15 sec

  Bridge ID  Priority    32832  (priority 32768 sys-id-ext 64)
             Address     1cdf.0f32.7200
             Hello Time   2 sec  Max Age 20 sec  Forward Delay 15 sec
             Aging Time  300 sec

Interface           Role Sts Cost      Prio.Nbr Type
------------------- ---- --- --------- -------- --------------------------------
Gi1/0/6             Desg FWD 4         128.6    P2p
Gi1/0/13            Desg FWD 4         128.13   P2p Edge

Thanks in advance!

[Jon Marshall · Accepted solution]

Do you mean make the root bridge for vlan 64 the 3750 ?

If so on the 3750 there are a couple of ways -

spanning-tree vlan 64 priority 8192

or

spanning-tree vlan 64 root primary

i've given you both ways as you may already have some of these type statements on your 3750.

Note, do not do this in office hours, schedule an outage as this will mean an STP reconvergence.

Jon

[dacruzer1]

Hi Jon,

Thanks much! 

How long do you think reconvergence will take for a VLAN?

Thanks again.

AL

[Jon Marshall]

If you are running standard STP then about 1 minute should do it but best to err on the side of caution.

Jon