vlans - stp state check

[suthomas1]

Hi All,

We will be deleting some vlans, creating new vlans & adding some current vlans to some trunk ports.
In terms of spanning-tree, what issues can this cause and what should be checked to verify stp is fine & there is no trouble started.

Appreciate all inputs. Thanks in advance.

[Reza Sharifi]

Deleting vlans is not an issue. When you add new vlans, add them to each device just like the existing vlans on that switch. For example; if a switch is root for all existing vlans configure the new ones the same way so there is consistency across all switches.

You can verify blocking and forwarding ports with "sh spann vlan xx"

Make sure to add the new vlans to trunk ports.

HTH

[suthomas1]

thank you for the reply.
we see below commands in our switch.

spanning-tree mode rapid-pvst
spanning-tree portfast default
spanning-tree portfast bpduguard default
spanning-tree extend system-id
no spanning-tree vlan 101,157,169,2001,3900
spanning-tree vlan 1-4094 priority 16384

We plan to add vlan 2001 & 3900 in the switches. Does it need anything else
(spanning-tree or so) to be configured when vlan 2001 & 3900 are added.

 & should the same command be used to verify the port states " sh spann vlan xx".

[Madhukrishnan Gopinathan Nair]

Hello,

Is there any reason you have disabled spannig for these vlans? As a best practise you should run spanning tree and not disable them.

no spanning-tree vlan 101,157,169,2001,3900

Thanks,

Madhu

[InayathUlla Sharieff]

Here is my answeR:-

spanning-tree mode rapid-pvst -- You are configured to run the rapid-pvst.

spanning-tree portfast default  -- This means that you want to avoid the delay time in bringing the ports of hte end stations immediately b eforgetting the STP states.

spanning-tree portfast bpduguard default  -- TO put the ports into Error-disabled when the portfast configured port recieved the BDDU.

no spanning-tree vlan 101,157,169,2001,3900  --> This means that you have disable the STP on this vlans.( when you run the command now

SW1#show spanning-tree vlan 101

No spanning tree instance exists.

you will get no STP instance) 

spanning-tree vlan 1-4094 priority 16384  --> This means you are manually setting the priority to be lower. ( Not sure if you are leaving the prioirty on the other switches to be default.)

Question:

=======

We plan to add vlan 2001 & 3900 in the switches. Does it need anything else
(spanning-tree or so) to be configured when vlan 2001 & 3900 are added.

Answer: There is no need of extra configuration of STP for these vlans. Define the vlans under the config and assign the respective ports to be part of these vlans.

 & should the same command be used to verify the port states " sh spann vlan xx". -- Yes.

HTH

Regards

Inayath

[suthomas1]

Thanks for the reply.

So, if vlan 2001 & 3900 are added to the vlan database, will the Stp instance for these be auto-created & not impacted by the "no spanning-tree vlan 101,157,169,2001,3900" statement, which exists?

( I am unsure why these were disabled-these have been in before i joined ).

I want to ensure there are no spanning tree issues for this.

[InayathUlla Sharieff]

Hi Suthomas,

When you have disabled the STP for those vlan then there is nothing which STP will do for those vlans for now. 

We would recommend you to enable the vlan and remove the vlans from the no spanning-tree so that we run the STP for those vlans. 

HTH

Regards

Inayath