10 Replies Latest reply: Dec 23, 2014 5:45 AM by Jon Major RSS

    Addition of a Vlan in port channel

    Paul George

      Dear Mates,

                  I have a case where i need to trunk a vlan through port channel .The set up is like there are two gig interfaces grouped as etherchannel and going to the device . There is confusion in adding the trunk as its very critical if the logical link breaks off. Guys please help me in th is regards.

       

      Regards,

       

        • 1. Re: Addition of a Vlan in port channel
          CiscoLoco - CCNP

          Just add "switchport trunk allowed vlan add (vlan tag)" under the port-channel interface. The same vlan changes will be added automatically to all physical interfaces that are part of the port channel.

          • 2. Re: Addition of a Vlan in port channel
            tnewshott

            Do the far-end first, and then the near end, and use the command posted above.  Problem solved.

             

            If you have redundant uplinks, be sure you are not changing the path you actually used to login to the device!!

            • 3. Re: Addition of a Vlan in port channel
              Bourbon, CCNP, CCIE Candidate

              If you don't already have any "allowed" or disallow commands on the port channel - then the vlan is already flowing through the trunk (unless you're pruning).

              • 4. Re: Addition of a Vlan in port channel
                Paul George

                Agreed to the answer that we need to add the vlan to port channel , what happens if we add to the gig interfaces ,why we are not adding there ,will it result in the breaking of the ether link .. can u just explain why we need to add this command to port channel not to the gig interfaces .

                • 5. Re: Addition of a Vlan in port channel
                  Inder Vaid

                  You can add one pair of link to etherchannel and if you are running STP like RSTP, then you can shutdown the link which is not on etherchannel, it will shift traffic within sub-millisecond to channel group link, then you can add the ports which were shutdown to etherchannel.

                  I did this on a link passing 1 gig channel without any single ping loss.

                   

                  HTH

                  Inder Vaid

                  • 6. Re: Addition of a Vlan in port channel
                    Paul George

                    I have one doubt ,when i have gone through one of the documents in cisco site its said that there is a command etherchannel guard to detect the misconfigured etherchannel interface.So my point here is that if this command is enabled will it detect the break of etherchannel links????? .As its said the immediate action in the interface is it will change to err disabled state.If it changes to this state its easy to restore i hope , will it works in the real scenario .????

                    • 7. Re: Addition of a Vlan in port channel
                      Inder Vaid

                      I am not sure about the command but if the etherchannel config is not matching on both ends or say between 2 physical interfaces on same router which you are adding in etherchannel, then etherchannel will not come up.

                      So have to be very careful when doing this on live traffic in business hours, in maintenance time that is least concerned but still

                      • 8. Re: Addition of a Vlan in port channel
                        Paul George

                        ya thanks ,i hope i need to do some labs to understand the real happening.... thanks to all

                        • 9. Re: Addition of a Vlan in port channel
                          mostapha

                          hi

                          i have a quisten according to the above

                          i configure allowed valn per interface physical on one swicth and i configure the other one per port-channel interface

                           

                           

                          and i notice the diffrent as the below althoug the same vlan allowed are used why are the active and prune valn are diffrent

                          Switch#show int trun

                          Port        Mode         Encapsulation  Status        Native vlan

                          Fa0/4       on           802.1q         trunking      1

                          Fa0/5       on           802.1q         trunking      1

                           

                          Port        Vlans allowed on trunk

                          Fa0/4       20-30,50

                          Fa0/5       20-30,50

                           

                          Port        Vlans allowed and active in management domain

                          Fa0/4       20,30,50

                          Fa0/5       20,30,50

                           

                          Port        Vlans in spanning tree forwarding state and not pruned

                          Fa0/4       20,30,50

                          Fa0/5       20,30,50

                          Switch#

                           

                          ------------------------------------------------------------------------

                           

                           

                          trunk feature activate per ether-channel

                           

                          Switch#show int trun

                          Port        Mode         Encapsulation  Status        Native vlan

                          Fa0/4       on           802.1q         trunking      1

                          Fa0/5       on           802.1q         trunking      1

                           

                          Port        Vlans allowed on trunk

                          Fa0/4       1-1005

                          Fa0/5       1-1005

                           

                          Port        Vlans allowed and active in management domain

                          Fa0/4       1,20,30,40,50

                          Fa0/5       1,20,30,40,50

                           

                          Port        Vlans in spanning tree forwarding state and not pruned

                          Fa0/4       1,20,30,40,50

                          Fa0/5       none

                           

                           

                          s

                           

                           

                          Switch#show int trun
                          Port        Mode         Encapsulation  Status        Native vlan
                          Fa0/4       on           802.1q         trunking      1
                          Fa0/5       on           802.1q         trunking      1
                          Port        Vlans allowed on trunk
                          Fa0/4       20-30,50
                          Fa0/5       20-30,50
                          Port        Vlans allowed and active in management domain
                          Fa0/4       20,30,50
                          Fa0/5       20,30,50
                          Port        Vlans in spanning tree forwarding state and not pruned
                          Fa0/4       20,30,50
                          Fa0/5       20,30,50
                          Switch#
                          ------------------------------------------------------------------------
                          trunk feature activate per ether-channel
                          Switch#show int trun
                          Port        Mode         Encapsulation  Status        Native vlan
                          Fa0/4       on           802.1q         trunking      1
                          Fa0/5       on           802.1q         trunking      1
                          Port        Vlans allowed on trunk
                          Fa0/4       1-1005
                          Fa0/5       1-1005
                          Port        Vlans allowed and active in management domain
                          Fa0/4       1,20,30,40,50
                          Fa0/5       1,20,30,40,50
                          Port        Vlans in spanning tree forwarding state and not pruned
                          Fa0/4       1,20,30,40,50
                          Fa0/5       none
                          s

                          • 10. Re: Addition of a Vlan in port channel
                            Jon Major

                            mostapha,

                             

                                 Your etherchannel is not active, so on the bottom switch your manual pruning isn't taking effect. I'm guessing you're using pagp or lacp to negotiate the etherchannel. If you apply 'switchport trunk allowed vlan x,y,z' on a port channel interface, that port channel interface has to actually be up in order for the configurations to take effect. Secondly, the "vlans in spanning-tree forwarding state' section, looks like on the bottom switch Fa0/4 is the root port and Fa0/5 is in blocking state.