addition of new vlan in Spanning tree in Nexus 7000

Answered Question
Jan 21st, 2010

Hi, I have two Nexus 7000 having VPC as trunk and VTP is in transparent mode.

Following vlans are aready created there having Spanning-tree priority and hello-timer defined. Please find the sw 1 conf below.

spanning-tree vlan 64-126,300-301,332,668-670,900,998 priority 8192

spanning-tree vlan 64-126,300-301,332,668-670,900,998 hello-time 4

interface port-channel1
  description SW2- Po1 - L2/TRUNK (vPC Peer Link)
  switchport
  switchport mode trunk
  switchport trunk native vlan 998
  switchport trunk allowed vlan 64-126,300-301,303,332-333,667-670
  switchport trunk allowed vlan add 888-889,900,998
  vpc peer-link
  spanning-tree port type network

NOW, I have created a new vlan 335 & I want to do the same thing. I am little bit worried, if new command will replace any current think. Please help, I have pasted below command which I m planning to run on current conf.

spanning-tree vlan 335 priority 8192

spanning-tree vlan 335 hello-time 4

interface port-channel1
     switchport trunk allowed vlan add 335

I have this problem too.
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Correct Answer by Giuseppe Larosa about 7 years 13 hours ago

Hello Rupesh,

use switchport trunk allowed vlan add 335

at port-channel interface only, both sides.

trying to add a vlan to a member link of an already established bundle is dangerous and can lead to bridging loops!!!

Hope to help

Giuseppe

Correct Answer by Ganesh Hariharan about 7 years 17 hours ago

So, you mean following command will not disturb/ override the current configuration .

spanning-tree vlan 335 priority 8192

spanning-tree vlan 335 hello-time 4

Hi Rupesh,

It clear from the above configuration and in your previous post that you are just configuring vlan 335 pirority to 8192,This means the switch will become the root bridge for this vlan 335 as the piroity is low as compare to other switches configuartion for this vlan 335.

Hope that clears out your query !!

Regards

Ganesh.H

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Ganesh Hariharan Thu, 01/21/2010 - 00:55

Hi, I have two Nexus 7000 having VPC as trunk and VTP is in transparent mode.

Following vlans are aready created there having Spanning-tree priority and hello-timer defined. Please find the sw 1 conf below.

spanning-tree vlan 64-126,300-301,332,668-670,900,998 priority 8192

spanning-tree vlan 64-126,300-301,332,668-670,900,998 hello-time 4

interface port-channel1
  description SW2- Po1 - L2/TRUNK (vPC Peer Link)
  switchport
  switchport mode trunk
  switchport trunk native vlan 998
  switchport trunk allowed vlan 64-126,300-301,303,332-333,667-670
  switchport trunk allowed vlan add 888-889,900,998
  vpc peer-link
  spanning-tree port type network

NOW, I have created a new vlan 335 & I want to do the same thing. I am little bit worried, if new command will replace any current think. Please help, I have pasted below command which I m planning to run on current conf.

spanning-tree vlan 335 priority 8192

spanning-tree vlan 335 hello-time 4

interface port-channel1
     switchport trunk allowed vlan add 335

Hi Rupesh,

It wont do any changes to your configuration for all other vlans as you have already configured the switch with low pirority 8192. And now you want this switch to be root with low pirority for this vlan by this command.

So switch will be root bridge for thsi vlan 335.

Hope that clear out your query!!

If helpful do rate the vlauable post.

Regards

Ganesh.H

Rupesh Kashyap Thu, 01/21/2010 - 01:08

So, you mean following command will not disturb/ override the current configuration .

spanning-tree vlan 335 priority 8192

spanning-tree vlan 335 hello-time 4

Correct Answer
Ganesh Hariharan Thu, 01/21/2010 - 01:15

So, you mean following command will not disturb/ override the current configuration .

spanning-tree vlan 335 priority 8192

spanning-tree vlan 335 hello-time 4

Hi Rupesh,

It clear from the above configuration and in your previous post that you are just configuring vlan 335 pirority to 8192,This means the switch will become the root bridge for this vlan 335 as the piroity is low as compare to other switches configuartion for this vlan 335.

Hope that clears out your query !!

Regards

Ganesh.H

Giuseppe Larosa Thu, 01/21/2010 - 04:27

Hello Rupesh,

if Nexus behaviour is similar to that of standard IOS switches you will see new vlan 335 added to the previous two command lines in the list of vlans.

In any case, even if showed as distinct lines, you are not affecting other STP instances configuration.

Also you need to add the vlan to the list of allowed vlan on port-channel as you have proposed in original post.

Hope to help

Giuseppe

Rupesh Kashyap Thu, 01/21/2010 - 04:31

Thanks Giuslar for your reply.

Should I allow vlan in Port-channel only or I have to allow this in respective attached interfaces too.

Ganesh Hariharan Thu, 01/21/2010 - 04:48

Thanks Giuslar for your reply.

Should I allow vlan in Port-channel only or I have to allow this in respective attached interfaces too.

Hi Giuseppe,

Thanks for pointing out the last point for allowing the vlan over the trunk.

Hi Rupesh,

As per the previous post you need to allow this vlan too in the trunk by following command switchport trunk allowed vlan add vlan number

Hope to help !!

Regards

Ganesh.H

Correct Answer
Giuseppe Larosa Thu, 01/21/2010 - 05:48

Hello Rupesh,

use switchport trunk allowed vlan add 335

at port-channel interface only, both sides.

trying to add a vlan to a member link of an already established bundle is dangerous and can lead to bridging loops!!!

Hope to help

Giuseppe

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