Re: Dual Homed Nexus 2Ks, 2950 on FEX HIF, and Spanning-Tree

Matt,
In normal scenario FEX 2000 can only be connected with the Parent switches
(n7k or n5k). These do not support STP.
These are the DCE (datacenter ehernet) switcehs.
see below:

Do not connect a bridge or switch to a host interface. These interfaces are
designed to provide end host or server connectivity.

http://cisco.biz/en/US/docs/switches/datacenter/nexus2000/sw/configuration/gu
ide/rel_4_1/Cisco_Nexus_2000_Series_Fabric_Extender_Software_Configuration_Gu
ide_chapter2.html

ic Extender Terminology

 Some terms used in this document are as follows:

   -

   Fabric interfaceA 10-Gigabit Ethernet uplink port designated for
   connection from the Fabric Extender to its parent switch. A fabric
   interface cannot be used for any other purpose. It must be directly
   connected to the parent switch.

   *Note*
   ------------------------------

   A fabric interface includes the corresponding interface on the parent
   switch. This interface is enabled when you enter the switchport mode
   fex-fabric command.
   ------------------------------
   -

   EtherChannel fabric interfaceAn EtherChannel uplink connection
from the Fabric
   Extender to its parent switch. This connection consists of fabric
   interfaces bundled into a single logical channel.
   -

   Host interfaceAn Ethernet host interface for connection to a server or
   host system.

   *Note*
   ------------------------------

   Do not connect a bridge or switch to a host interface. These interfaces
   are designed to provide end host or server connectivity.
   ------------------------------

  Fabric Extender Features

On Sun, May 30, 2010 at 4:25 AM, Wes Stevens
<wrsteve33-gsccie_at_yahoo.com>wrote:

> You cant plug a 2950 into a fex port.
>
> --- On Sat, 5/29/10, Matt Bentley <mattdbentley_at_gmail.com> wrote:
>
>
> From: Matt Bentley <mattdbentley_at_gmail.com>
> Subject: Dual Homed Nexus 2Ks, 2950 on FEX HIF, and Spanning-Tree
> To: "Cisco certification" <ccielab_at_groupstudy.com>
> Date: Saturday, May 29, 2010, 10:35 AM
>
>
> *Hi Group:*
> *
> *
> *I have a question about running spanning-tree on the Nexus switches.*
> *
> *
> *Basically, I am trying to get working a setup similar to this one (see
> page
> 27 of the PDF). The difference being that the HIF (FEX Downlink) port is
> plugged into a 2950 switch. No traffic is able to get to or from the 2950
> switch - because I believe of spanning-tree issues*
>
> *
>
>
http://www.cisco.com/en/US/prod/collateral/switches/ps9441/ps9670/C07-572829-
>
01_Design_N5K_N2K_vPC_DG.pdf<http://www.cisco.com/en/US/prod/collateral/switc
hes/ps9441/ps9670/C07-572829-%0A01_Design_N5K_N2K_vPC_DG.pdf>
> *<
> http://www.cisco.com/en/US/prod/collateral/switches/ps9441/ps9670/C07-57282
>
9-01_Design_N5K_N2K_vPC_DG.pdf<http://www.cisco.com/en/US/prod/collateral/swi
tches/ps9441/ps9670/C07-57282%0A9-01_Design_N5K_N2K_vPC_DG.pdf>
> >
>
> *Per below, you see that the same FEX port E122/1/48 is showing up on both
> Nexus switches. However, it appears like the Nexus's are having
> spanning-tree problems (Dispute P2P). At this point, I think it's because
> both NX01 and NX02 are sending spanning-tree BPDUs to it. I thought that I
> could "unify" the control planes of these switches by putting e122/1/48 on
> both Nexus switches into the same port-channel - I guess this is with the
> assumption that the problem is caused by both Nexus switches sending
> BPDUs.*
>
> *However, when I attempt to do it, I get this error. *
>
> *NX-01(config-if)# interface Ethernet122/1/48*
> *NX-01(config-if)# channel-group 267 mode active *
> *Fabric in Fex A-A mode, can't configure sat port as member*
>
> *After researching, it appears like the Nexus will not allow HIF (FEX
> Downlink) ports to be placed in a port-channel when a FEX (in this case
> 2148) is dual-homed to two Nexus 5Ks. Most Cisco documentation uses
> different FEXs. *
>
> *
>
>
https://supportforums.cisco.com/message/469676;jsessionid=61093138BE6B928721E
> 471BF442AA85D.node0
> *<
> https://supportforums.cisco.com/message/469676;jsessionid=61093138BE6B92872
> 1E471BF442AA85D.node0>
> *That's my understanding also, you can only do port channels to the host
> when you use a single connection from two different single homed FEX's
> (using vPC).*
> *
> *
> *I've read a few things about spanning-tree bridge assurance, but was
> curious if anyone had encountered this before. Any comments would be most
> helpful. Thank-you.*
> *
> *
> *NX-01# show spanning-tree vlan 27*
> *VLAN0027*
> * Spanning tree enabled protocol rstp*
> * Root ID Priority 8219*
> * Address 0000.0000.0000*
> * Cost 3*
> * Port 4128 (port-channel33)*
> * Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec*
> *
> *
> * Bridge ID Priority 32795 (priority 32768 sys-id-ext 27)*
> * Address 0000.0000.0000*
> * Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec*
> *
> *
> *Interface Role Sts Cost Prio.Nbr Type*
> *---------------- ---- --- --------- --------
> --------------------------------*
> *Po33 Root FWD 1 128.4128 (vPC peer-link) Network P2p *
> *Eth1/1 Altn BLK 2 128.129 P2p *
> *Eth1/2 Altn BLK 2 128.130 P2p *
> *Eth1/3 Desg FWD 4 128.131 P2p *
> *Eth1/4 Desg FWD 4 128.132 P2p *
> *Eth1/14 Desg FWD 4 128.142 P2p *
> *Eth120/1/26 Desg FWD 1 128.3098 (vPC) Edge P2p *
> *Eth121/1/18 Desg FWD 1 128.3218 (vPC) Edge P2p *
> *Eth122/1/48 Desg BLK 1 128.3376 (vPC) P2p *
> *
> *
> *
> *
> *
> *
> *NX-02# sh spanning-tree vlan 27*
> *VLAN0027*
> * Spanning tree enabled protocol rstp*
> * Root ID Priority 8219*
> * Address 0000.0000.0000*
> * Cost 2*
> * Port 129 (Ethernet1/1)*
> * Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec*
> * Bridge ID Priority 32795 (priority 32768 sys-id-ext 27)*
> * Address 0000.0000.0000*
> * Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec*
> *Interface Role Sts Cost Prio.Nbr Type*
> *---------------- ---- --- --------- --------
> --------------------------------*
> *Po33 Desg FWD 1 128.4128 (vPC peer-link) Network P2p *
> *Eth1/1 Root FWD 2 128.129 P2p *
> *Eth1/2 Altn BLK 2 128.130 P2p *
> *Eth1/3 Desg FWD 4 128.131 P2p *
> *Eth1/4 Desg FWD 4 128.132 P2p *
> *Eth1/14 Desg FWD 4 128.142 P2p *
> *Eth120/1/26 Desg FWD 1 128.3098 (vPC) Edge P2p *
> *Eth121/1/18 Desg FWD 1 128.3218 (vPC) Edge P2p *
> *Eth122/1/48 Desg BLK 1 128.3376 (vPC) Dispute P2p *
>
>
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Received on Sun May 30 2010 - 16:02:47 ART