[Okta Webinar] Learn how to a build a cloud-first strategyRegister Now

x
  • Status: Solved
  • Priority: Medium
  • Security: Public
  • Views: 955
  • Last Modified:

Cisco 3750-X Spanning Tree Root/Priority

hi there.... just curious... how should i configure my Cisco 3750-X as STP root...?
can i configure in global..?

thanks
0
hell_angel
Asked:
hell_angel
  • 3
  • 3
1 Solution
 
jigardaveCommented:
Globally you need to specify,
 spanning-tree vlan vlan-id root primary. vlan-id is vlan number
"The spanning-tree vlan vlan-id root global configuration command fails if the value necessary to be the root switch is less than 1".  means check other switch which is root and change it's vlan's spanning tree value.
As per Cisco command is spanning-tree vlan vlan-id root primary [diameter net-diameter [hello-time seconds]]
0
 
Don JohnstonInstructorCommented:
config t
spanning-tree <vlan number> priority <numeric value>
end

For the numeric value, it should be lower than any other switch. The default is 32768 so unless you've changed any other switches, lower than that will make your switch the root. Also, it now has to be in multiples of 4096. So just changing it to 32767 won't work (anymore). Setting it to 4096 is about as low as you can go so that value will almost insure that the switch is the root... Unless another switch has it's priority set to that value. Then it will fall to the MAC address of the switch.

Or, as previously mentioned, you could use the command:

spanning-tree <vlan number> root primary

This will look at the priority of the current root and attempt to be lower.
0
 
hell_angelAuthor Commented:
im abit puzzle.... why need to put VLAN ID...? can put vlan 1..???
0
What does it mean to be "Always On"?

Is your cloud always on? With an Always On cloud you won't have to worry about downtime for maintenance or software application code updates, ensuring that your bottom line isn't affected.

 
Don JohnstonInstructorCommented:
Because Cisco uses "Per VLAN" spanning tree. Each VLAN has it's own instance of spanning-tree. So just about any spanning-tree configuration command has to include the VLAN. This way, you can have one switch be the root of say VLAN 5 but not be the root of VLAN 6.

If you only have on VLAN (VLAN 1) then you could use the command "spanning-tree 1 priority 16384".
0
 
hell_angelAuthor Commented:
does it meant if the switch will act as core switch, and i should run the spanning tree command for multiple vlan..?
0
 
Don JohnstonInstructorCommented:
If you have multiple VLANs and you want this switch to be the root for all of them, then you will need to issue the command for each vlan.

spanning-tree 1 priority 4096
spanning-tree 20 priority 4096
spanning-tree 25 priority 4096
spanning-tree 26 priority 4096
etc.
0
 
hell_angelAuthor Commented:
Ok... this should clear my doubt... i read the doc this morning... total lost....
0

Featured Post

Technology Partners: We Want Your Opinion!

We value your feedback.

Take our survey and automatically be enter to win anyone of the following:
Yeti Cooler, Amazon eGift Card, and Movie eGift Card!

  • 3
  • 3
Tackle projects and never again get stuck behind a technical roadblock.
Join Now