Spanning Tree VLAN Priority Issue

[datamodule]

We have two 6500E switches and running spanning tree with rapid-pvst.We have also configured per vlan spanning tree priority with 100,200 so odd vlan have one switch hight priority and even vlans have  another switch high priority.

I have created new vlan 10 and tring to add spanning tree priority to the switches i am getting the following error

Core-switch(config)#spanning-tree vlan 10  priority 100
% Bridge Priority must be in increments of 4096.
% Allowed values are:
  0     4096  8192  12288 16384 20480 24576 28672
  32768 36864 40960 45056 49152 53248 57344 61440

Can some experts help me why i am getting the above message and how can i add the priority to the same as existing vlans

[Dragan Ilic]

That's perfectly normal info you get there - priority is always in 4096 increment step. So configure one of the proposed values and you are ready to go...

Also check your priority values on other vlans - i'm pretty sure you are not going to see 100, 200... values there - but also 4096 step one.

See output of "show spanning vlan..." and that will give you an answer...

BR,

Dragan

[datamodule]

Thanks for your reply i have spanning tree priprity vallues set to odd vlans to 25 and even vlans to 2500 (not 100,200)

The working ones are

spanning-tree vlan 703,705,801,999 priority 25

spanning-tree vlan 490,500,556,622,624,700,702,800,900 priority 2500

The issue is i have created new vlan 189 and adding to spanning tree priority 2500 using the following command i am getting the same error

Core-switch(config)#spanning-tree vlan 189  priority 2500
% Bridge Priority must be in increments of 4096.
% Allowed values are:
  0     4096  8192  12288 16384 20480 24576 28672
  32768 36864 40960 45056 49152 53248 57344 61440

[Dragan Ilic]

Please give me output of "show spanning vlan 490" to check that?

BR,

Dragan

[datamodule]

VLAN0490
  Spanning tree enabled protocol rstp
  Root ID    Priority    490
             Address     d824.bd90.4000
             This bridge is the root
             Hello Time   2 sec  Max Age 20 sec  Forward Delay 15 sec

  Bridge ID  Priority    490    (priority 0 sys-id-ext 490)
             Address     d824.bd90.4000
             Hello Time   2 sec  Max Age 20 sec  Forward Delay 15 sec
             Aging Time 300

[datamodule]

Fro VLAN 189 i am getting the following output which seems to be strange

VLAN0189
  Spanning tree enabled protocol rstp
  Root ID    Priority    32768
             Address     0018.7438.f8bd
             Cost        2
             Port        898 (TenGigabitEthernet8/2)
             Hello Time   2 sec  Max Age 20 sec  Forward Delay 15 sec

  Bridge ID  Priority    32957  (priority 32768 sys-id-ext 189)
             Address     d824.bd90.4000
             Hello Time   2 sec  Max Age 20 sec  Forward Delay 15 sec
             Aging Time 300

[Dragan Ilic]

Look at this row:

for VLAN 490 - Bridge ID  Priority    490    (priority 0 sys-id-ext 490) - it seems that priority for this VLAN is 0 plus the sys-id-ext which is 490

for VLAN 189 - Bridge ID  Priority    32957  (priority 32768 sys-id-ext 189) - this looks normal because default priority is 32768 + sys-id-ext 189 which is fine.

So - it seems that your VLAN 490 is someway defined with priority 0...

What IOS is this on 6500E?

BR,

Dragan

[datamodule]

Thanks for that and why it shows priority as 2500 for vlan 490

Version 12.2(33)SXI3, RELEASE SOFTWARE (fc2)

We are defining per vlan spanning tree priority for odd and even vlans to load balance the traffic between two core switches

[Dragan Ilic]

For VLAN 490 you have priority 490 btw...

Can you give output of "sho run | i spanning" please...

BR,

Dragan

[datamodule]

Requested command output as follows

spanning-tree mode rapid-pvst
no spanning-tree optimize bpdu transmission
spanning-tree extend system-id

spanning-tree vlan 703,705,801,999 priority 25

spanning-tree vlan 490,500,556,622,624,700,702,800,900 priority 2500

In the last two command we have more vlans so i just gave less

[Dragan Ilic · Accepted solution]

OK it's fine for showing just few of VLANs...well I can only conclude that your switch accepts this command "spanning-tree vlan 490,500,556,622,624,700,702,800,900 priority 2500" but it shouldn't - it should give you warning about 4096 increment step.

Anyway, for those VLANs it seems like switch accepted your values but because they are lower than 4096 - switch give them priority of 0.

And because you are using extend system-id functionality with spanning-tree switch add vlan number to defined priority - so for vlan 490 you have 0+490=490 and for vlan 189 you have 32768+189=32957.

BR,

Dragan

[datamodule]

The reason for the commands are not working previously is because of "spanning-tree extend system-id"

So some one added that command so from now on it will take 4096 increment

[SANTHOSHKUMAR SARAVANAN]

Hi ,

 Spanning tree priority can be set in increment of 4096 , any other values will be rejected . if you want to know about priority value of existing vlan execute command show spanning-tree vlan X / show spanning-tree command which will show you switch priority value 

Step 2

spanning-tree vlan vlan-idpriority priority

Configure the switch priority of a VLAN. •For vlan-id, you can specify a single VLAN identified by VLAN ID number, a range of VLANs separated by a hyphen, or a series of VLANs separated by a comma. The range is 1 to 4094. •For priority, the range is 0 to 61440 in increments of 4096; the default is 32768. The lower the number, the more likely the switch will be chosen as the root switch. Valid priority values are 4096, 8192, 12288, 16384, 20480, 24576, 28672, 32768, 36864, 40960, 45056, 49152, 53248, 57344, and 61440. All other values are rejected.

HTH

Sandy