4 Replies Latest reply: Oct 8, 2010 7:20 AM by Cyianara69 RSS

Nexus 1000v and vPC on Nexus 5k




One Esxi host with two 2 port 10g CNAs and two Nexus 5k switches up stream.


One port of the CNAs are cable into the Nexus 5k and the following configs are place on the respective switches


Nexus 1kv


port-portfile type ethernet network-uplink
vmware port-group
switchport mode trunk
switchport trunk allowed vlan all
system vlan 411-412
channel-group auto mode active
no shutdown
state enabled


Nexus 5K a & b


interface port-channel10
swtchport mode trunk
vpc 10
spanning-tree port type edge trunk
speed 10000


interface ethernet1/10
switchport mode trunk
spanning-tree port type edge trunk
channel-group 10 mode active


For some odd reason, the port-channel on the Nexus 5kb flapping consistently.


Any suggestions??  Thanks.

  • 1. Re: Nexus 1000v and vPC on Nexus 5k

    Hi Cy,


    With LACP configurations we have the recommendation of having the portfast, bpdufilter and bpduguard configuration on both individual interfaces and the port channels on the upstream switch, check if adding those give you any better results. You can also check for mode passive on the N1K side.


    Additionally if there are no specific reasons for using vpc on the n5k for the N1k host, you can also look at the mac-pining option since you have 10 GB interfaces.




  • 2. Re: Nexus 1000v and vPC on Nexus 5k

    I already had portfast running and have enabled bpdufilter and bpduguard on both the 5Ks and it didn't help.  One thing that is strange is that I will have the port-channel configured on the 5k and not on 1k and all my traffic is switched properly.  However when I turn on port-channel on the 1k with mode passive or active, all my traffic dies.  If I  make the 1k active and the 5k passive and all my traffic starts being switch.  However when I do a port-channel sum command, I see my two interfices on the 1k as Eth3/2(I) Eth3/4(I) .... normally I would think they should be Eth3/2(P) Eth3/4(P) .....


    Also, not sure if this related to the following, when I shut down my primary 5K interface to 1k, the VEM powers down from the 1k ...... the VEM powers back on when I bring the port back up.


    Any thoughts?

  • 3. Re: Nexus 1000v and vPC on Nexus 5k

    So you have two connections from the VEM to the upstream switch or switches? So 3/2 goes to N5K-A and 3/4 goes to N5K-B? Or do both VEM connections go to the same N5K? I see you have VPC defined so I'm assuming its different switches but want to be sure.


    If you are shutting down the port-channel the VEM is going to drop. You've essentially killed the virtual backplane between the VEM and the VSM. If you have killed just one connection of the port-channel then that should not happen.


    In your output below the interfaces are in the I state that means Individual. They should be in the A state for active. I beleive but am not certain that if they are in the I state the port-channel is not really up. Traffic is only flowing over one link and the other link is not available for failover.


    Could you verify that your VPC configuration is correctly configured on the N5K? What you can try is to create port-channel without LACP between then N1K and N5K by using "channel-group auto mode on" on both sides. If that works then VPC should be correct on the N5K.



  • 4. Re: Nexus 1000v and vPC on Nexus 5k

    Putting the port channel mode in the on mode fixed my problem it looks like.  Both ports on 1K are in the port channel now and the single port on each of the 5k are also in the port channel.


    Traffic is flowing out of the 1K like it should be ... thanks.