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

This is because the N2K design...it has BPDU hard code filtering...can't
cascade a switch into the 2148,2248,...

You will have to go straight to the N5K (non-vpc portchannel).

Regards

2010/5/30 Radioactive Frog <pbhatkoti_at_gmail.com>

> 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 interface A 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 interface An EtherChannel uplink connection
> from the Fabric
> Extender to its parent switch. This connection consists of fabric
> interfaces bundled into a single logical channel.
> -
>
> Host interface An 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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-- 
G.Ruiz
Blogs and organic groups at http://www.ccie.net