NXOS - IOS / BPDU sending on edge port type

[krahmani323]

Hello community,

I am wondering about one thing that surprising me :

On a 6500 IOS I have an access port configured as an access port as "spanning-tree portfast edge"

I can notice the continuous sending of BPDU through the interface :

******** On the 6500 ********

show spanning-tree interface GiX detail    

   The port is in the portfast edge mode

   BPDU: sent 4414440, received 0

*********************************************

But on a similar interface of a N2K host interface of a 5548 w/2248T in 5.0(3)N1(1c) =>

******** On the Nexus ********

interface Ethernet 100/1/1

  spanning-tree port type edge

  spanning-tree bpduguard enable

  no spanning-tree bpdufilter

(=> Which is the default on a HIF).

*********************************************

I do not see any incrementation for the sending of BPDUs =>

*********************************************

Nexus5k # sh spanning-tree interface ethernet 116/1/18 detail

Port YYYY (Ethernet100/1/1, vPC) of VLAN0010 is designated forwarding

   Link type is point-to-point by default

   Bpdu guard is enabled

   Bpdu filter is enabled by default (???)

   BPDU: sent 11, received 0

*********************************************

My question is : Are BPDU sent through from FEX host interface ? 

It looks like the hif interfaces are acting as if bpdufilter was enabled (bpdu not sent neither processed) although it is by default [globally + per interface] disabled.. 

Globally

Port Type Default                        is edge

Edge Port [PortFast] BPDU Guard Default  is enabled

Edge Port [PortFast] BPDU Filter Default is disabled

Thanks for your suggestions !!

Regards

Karim

[Jerry Ye · Accepted solution]

The reason why bpdu counter is not incrementing is bpdufilter is enabled. And HIF of the FEX has bpdufilter enabled by default.

HTH,

jerry

[krahmani323]

Hi Jerry,

Thank you, I got it know...!

http://www.cisco.com/en/US/prod/collateral/switches/ps9441/ps9670/C07-572829-01_Design_N5K_N2K_vPC_DG.pdf

(page38)

BPDU Filtering on Host Ports

BPDU filtering increases the scalability of the Layer 2 topology and reduces the load on the server for processing control-plane traffic.

A host port configured on Cisco Nexus platforms for BPDU filtering sends out 10 BPDUs at link up. If no response follows, the port assumes that the device connected to it is a server, and as a result the port stops sending BPDUs to the device.

On Cisco Nexus 2000 Series ports, BPDU filtering is enabled by default as shown by the command show spanning-tree interface detail.

In fact the below 'show run' output was disturbing me but now it makes sense for me.

On my FEX interface

interface Ethernet 100/1/1

  spanning-tree port type edge

spanning-tree bpduguard enable

  no spanning-tree bpdufilter  <==========================

Thanks and regards.

Karim