6 Replies Latest reply: Feb 21, 2017 12:42 AM by Juan RSS

    Could an HSRP router/switch forward traffic?

    Malik

      Hi guys! wish your alright.


      I have a small question about the HSRP behavior. I configured 2 switches (Cat 3650) for load sharing with hsrp :



      Switch 1 : active for vlan 90,999 and standby for the rest

       

      Switch 2 : active for vlan 200, 300 and standby for other vlans.

       

      So I had some strange behavior when i tried to follow my traffic, The standby router for vlan 90 (switch2) is the principal forwarder.... And when i unplug the cable the traffic goes to the supposed active switch.

       

      I am aware that i have no tracking object.

       

      But my question is how it comes that a standby switch can forward traffic???

       

       

      Thank you in advance.

        • 1. Re: Could an HSRP router/switch forward traffic?
          Anthony

          Malik wrote:

           

          So I had some strange behavior when i tried to follow my traffic, The standby router for vlan 90 (switch2) is the principal forwarder.... And when i unplug the cable the traffic goes to the supposed active switch.

          Can you describe this in a bit more detail.  For instance, did you traceroute from an end station attached to VLAN 90 and the first hop report included the physical IP address of switch2?  Could you put together a quick diagram that shows the traffic flow that you observed vs. expected?  That might help this conversation.

          • 2. Re: Could an HSRP router/switch forward traffic?
            Juan

            Hi Malik ,

             

            So I had some strange behavior when i tried to follow my traffic, The standby router for vlan 90 (switch2) is the principal forwarder.... And when i unplug the cable the traffic goes to the supposed active switch.

             

            Strange description. I understand you are trying to implement VLAN load balancing with STP and HSRP in an access/distribution setup in which you configured the STP root and HSRP primary in sync to be Switch 1 for VLANs 90 and 999 and Switch 2 for VLAN 200 and 300. That´s right?

             

            If that is the case, your traffic should follow the path to the HSRP active (STP root).

             

            Could you post a diagram of your setup and perhaps some configuration of STP and HSRP? This could lead to spot the problem.

             

            Best regards !

            • 3. Re: Could an HSRP router/switch forward traffic?
              Ramon G.

              Hi! Malik. Please take in consideration what Juan pointed, for optimum path selection you should configured the HSRP active switch for the intended vlan as the STP root for that vlan, if the scerario is different than this then you may see suboptimal forwarding path within the domain.

              • 4. Re: Could an HSRP router/switch forward traffic?
                Malik

                Hi juan, thank you for the answer.

                 

                You were right, the spanning tree was the problem, I misconfiured it or i did something wrong. in my design i had only one ROOT for all the vlans, so when you talked about the spanning tree, I checked the config and found the problem. (The standby Switch was the root bridge for every vlan)

                 

                Thank you very much for your answer.

                 

                And sorry for the late, my wife gave birth the day after i posted this. ^^

                 

                Best regards.

                • 5. Re: Could an HSRP router/switch forward traffic?
                  Malik

                  Hi,

                   

                  Found it, it was a misconfiguration i did in Spanning tree. Switch 2 was the root bridge for the whole topology.

                   

                  Thank you for your answer.


                  Wish you luck

                  • 6. Re: Could an HSRP router/switch forward traffic?
                    Juan

                    HI Malik, great news.

                    See you around.

                     

                    Best regards !