BPDU Errors

[jay01]

Hi,

I have an ICX edge switch connected to Core using 802.1w.  I need to uplink another extreme switch to the existing ICX edge switch.  
Vlan 900 is configured on the extreme switch this vlan has configured with spanning-tree 802.1w and stp for point to point link to core on the ICX switch.Currently when RSTP enabled on extreme switch I am getting BPDU Errors:-

STP BPDU Drop messages flooding the logErro:STP.

InBPDU.Drop Port=24 ! STP Port is disabled!

Is there some additional configuration required on iCX switch to stop the BPDU errors ?

[Chandini]

Hi Jay 

Thank you for reverting back to us. 

Please prefer configuring  admin-pt2pt-mac at the interface level between interfaces of the two switches. Below is the command.

• Device(config)#int e 1/1/1
  
• Device(config-if-e1000-1/1/1)#spanning-tree 802-1w admin-pt2pt-mac
  

Thanks 

[jay01]

Hi Chandini,

What is the difference between configuring admin-pt2pt-mac on interface level compared with configuring under a vlan.   Is that effectively like vlan pruning?

Say for example the ports where in a lag and tagged to lag20 under vlan 100. Can the pt2pt command be applied to both interface and under vlan 100 at the same time ? 

[Chandini]

Hi Jay 

Thanks for reverting. I ran a quick test and below is the difference I could find. 

Enabling admin-pt2pt-mac in interface:
ICX7150-48PF Router(config-if-e1000-1/1/1)#spanning-tree 802-1w
admin-edge-port Declare the port to be an operational edge for all vlans
admin-pt2pt-mac Declare the port to be on a Pt2Pt link for all vlans

Enabling admin-pt2pt-mac in vlan:
ICX7150-48PF Router(config-vlan-2)#spanning-tree 802-1w e 1/1/1 admin-pt2pt-mac
admin-edge-port Declare the port to be an operational edge
admin-pt2pt-mac Declare the port to be on a Point-to-Point link

Example :

When admin-pt2pt-mac is enabled in interface level:

When admin-pt2pt-mac is enabled in vlan level:

From above two examples you can note on the difference that when enabled in vlan you can see only P2P Mac counter for vlan 200 only enabled as True applying only to that vlan. Whereas when enabled on interface level you can note that the P2P Mac counter for vlan 200 and vlan 300 is enabled as True.

Hence when enabled on interface level the port is recognized as a point to point link for all vlans where the port is mapped as tagged or untagged interface. And when enabled on vlan alone it is recognized only by that vlan as point to point interface based on above test. 

Hence it is recommended to enable admin-pt2pt-mac on a interface rather than a vlan. 

I hope this answers your question. 

Thanks 

[jay01]

Hi Chandini,

Thank for response.  Yes the switch configuration I have has STP configured on vlans not sure of the reason but I only have worked with Cisco.

Do you by chance have sample config of a Core switch with RSTP configured and one for Edge switch please ?   It will provide me with a template?

[Chandini · Accepted solution]

Hi Jay 

Thank you for reaching. Sorry but I don't have a template but below is a example. I hope this helps. 

Topology :

• Core Switch p2p connection (1/1/1) -> p2p connection (1/1/1) Access Switch (1/1/2) -> end device
• Consider both switches have vlan 1 , vlan 2 and vlan 3
• 1/1/2 is end device part of vlan 3 only

If above scenario is considered below would be the configuration:

For core switch: 

Vlan configuration:

• Device(config)#vlan 1 2 3
• Device(config-mvlan-1-3)#spanning-tree 802-1w
• Device(config-mvlan-1-3)# spanning-tree 802-1w priority 4096  // note this priority you can consider based on your network topology
• Device(config)#vlan 2 3
• Device(config-mvlan-2-3)#tagged e 1/1/1

Port configuration:

• Device(config)#int e 1/1/1
  
• Device(config-if-e1000-1/1/1)#spanning-tree 802-1w admin-pt2pt-mac
  

For access switch: 

• Access(config)#vlan 1 2 3
• Access(config-mvlan-1-3)#spanning-tree 802-1w
• Access(config)#vlan 2 3
• Access(config-mvlan-2-3)#tagged e 1/1/1
• Access(config)#vlan 3
• Access(config-vlan-3)# untagged e 1/1/2

Port configuration:

• Access(config)#int e 1/1/1
  
• Access(config-if-e1000-1/1/1)#spanning-tree 802-1w admin-pt2pt-mac
• Access(config)#int e 1/1/2
  
• Access(config-if-e1000-1/1/2)#spanning-tree 802-1w admin-edge-port

I hope the above details help you

Thanks