2 Replies Latest reply on Jun 18, 2019 5:35 AM by robertwebb

    Adding vlan to trunk on switch kills all traffic

    robertwebb Novice

      We are running 2 cisco nexus 9K switches as aggregation switches and vPC links between them. We have 5 vsphere hosts up and running on trunks and virtual networking is configured into DVS from VCenter. We have two vlans configure on the switch side trunk and two port groups on the DVS side up and passing traffic.


      Weird issue happened today after I added a vlan to the switch side trunks, all traffic stopped passing. None of the previously accessible VM's were able to be reached. Removed the new vlan on the switch side and all VM's were again accessible.


      I am using Cisco DCNM to add the vlan to to the port channel and vpc and after adding, all the vpc statuses are showing as good and up successfully. I manually verified on both switches through ssh that the vlan existed on both switches, the vlan was up, and show vpc along with show vpc global commands were good.


      Is there something I could be missing config wise on the DVS when it receives an unknown vlan tag that is starts blocking all traffic? I was previously certified but has been a long time since I have had to dive in and we are now running 6.7. I now have to depend on someone who is not knowledgeable at all to do the config and screen shares to try and figure this out so it makes it quite difficult.


      Any thoughts??