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Community Member

Discovered an annoying bug creating vPC FEX-to-Hosts

Hi there,

First of all, thanks a lot Lucien. You are the best!

Well, I´ll be brief:

I thought, that vPC from FEX-to-Hosts work as vPC between N5K-to-FEX does. You create the Port-channel, and you move it to vPC manually.

But it´s not, from FEX-to-Host you gotta configure just the Port-channel, and then, that Port-channel is internally assigned to a vPC. Easier. That´s fine.

PROBLEM: When I removed the vpc commands underneath of the FEX-to-Host Portchannels, I realized that although the internal vPC look healthy now (up and successfull), I can still see old vPC after executing SHOW VPC:

1004   Po1004      up     Not         Consistency Check Not      -

                          Applicable  Performed

263147 Po1004      up     success     success                    1-2,7-8,10-





If I create new Port-channels, just internal vPC show up.

I believe this is a bug, and there is no easy way to clear up the old/utilized vPC. I tried to #clear vPC and so forth, but no luck.

what can i tell to my customer? any chance to have this fixed?

NX-OS are updated to the last version (1month ago)

kickstart image file is: bootflash:///n5000-uk9-kickstart.5.1.3.N2.1.bin

  kickstart compile time:  3/20/2012 0:00:00 [03/20/2012 08:51:29]

kickstart: version 5.1(3)N2(1)

  system:    version 5.1(3)N2(1)

Thanks a lot everyone,

Cisco Employee

Discovered an annoying bug creating vPC FEX-to-Hosts

Hello Josu

I can test this in my lab. So let me know if I understand the sequence of operations correct.

1)You created interface Po1004 and then added vpc 1004 under it on both Nexus 5500s

interface Port-channel1004

vpc 1004

2)You tried adding "channel-group 1004" to A/A FEX interfaces but it failed.

3)You removed vPC keyword under "interface Port-channel1004" but show vpc command still shows vPC 1004



Community Member

Discovered an annoying bug creating vPC FEX-to-Hosts

Thanks a lot prkrishn,

1.- Find attached a network diagram

2.- Sequence is like this:

You create a a vPC from two different FEX to a Host like this:

                                interface Ethernet101/1/4

          switchport mode trunk

          channel-group 1004

                                interface Ethernet102/1/4

          switchport mode trunk

          channel-group 1004

Then you assign a vpc to the channel-group

                                interface po1004

          vpc 1004           <-- this is wrong, triggering the problem. I shouldn’t have typed that.

If I do a SHOW VPC, I can see both vPC id: 1004 and Internal vpc, for instance, 123324, pointing at the Po1004. Only the internal one is SUCCESS.

Now, even though I clear up “vpc 1004”, both vPC id still appear when SHOW VPC

If I create a brand new Port-Channel, works fine. Just internal vPC is created.


You can also ring me: +34 634 645 001

Cisco Employee

Discovered an annoying bug creating vPC FEX-to-Hosts

Hi Josu

I tried from config t and conf sync as well and cannot recreate the problem. If you can, let me know the steps or we can set up a webex.



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