1 2 Previous Next 21 Replies Latest reply on Nov 23, 2017 1:00 AM by rajeevsrikant Go to original post
      • 15. Re: NSX Edge - ECMP
        Preetam Zare Expert

        Dear Rajeev,


        Please review with your management team how much downtime is acceptable.

        If they cannot accept 30 sec downtime, I could imagine incorrect mapping of requirement into the design implementation.

        Please review design guide to modify Hello Interval and dead time interval when you deploy ECMP

        With Great Regards,
        vExpert 2012-2017 | VCP3-5 | VCAP5-DCD | VCP-NV | vSAN Specialist | VDI | Germany
        • 16. Re: NSX Edge - ECMP
          rajeevsrikant Expert
          vExpertCommunity Warriors


          I can not have down time for this activity

          That is for sure.

          Also my previous experience is as below.


          ECMP was enabled

          I changed the OSPF cost of one of the NSX Edge Gateways uplinks from 1 -> 100

          No OPSF cost change was done at the router side.


          With the above I experienced packet loss & network disconnection.

          • 17. Re: NSX Edge - ECMP
            ASIS_Intl Novice

            This is the correct answer, I believe. Sessions will not renegotiate their path based on the routing cost changes, but new sessions will use just the active path. To achieve no downtime you would need to make the changes you describe some time before the maintenance window and monitor the active flows on the no-longer-routable-but-still-active link. Eventually, the flows should go down to nothing and then you could either proceed with disabling the inactive uplink on the ESG and/or proceed directly to completing the maintenance.


            edit - it appears I didn't read every post. Oops. I would guess you had packet loss because ECMP was still enabled on the ESG - thus the ESG is still trying to send packets out of both of the active links while OSPF is screaming not too. I'm actually unsure on your options in that scenario - is there no VMware KB or doc that explains how to handle this situation? Hmmm.


            edit2 - I will try testing this scenario in a lab later today if I have a few minutes. Should be fairly easy to replicate with my current setup.

            • 18. Re: NSX Edge - ECMP
              Mparayil Enthusiast

              Based on my understanding you want one link to be as a stantBy and one to be active


              1) changing the Cost to 1 for the Primary link and increase the cost for the standby link

              2) change the Hello timers to 1/3

              3) disable the Grace full restart from all the devices so any ospf reset or restart of the router will flush the routing table you may notice 1 ICMP drop.



              or you can have one link with default route towards your Physical router with increased AD value so when the OSPF is down with primary link it use the other standby link

              • 19. Re: NSX Edge - ECMP
                Preetam Zare Expert

                There is absolutely no need to change the OSPF cost. It is not the right approach.

                As Sreec mentioned it will apply unequal paths and bring more downtime.

                Instead as suggested earlier change hello interval which are neatly described in NSX design guide.


                ECMP is for near zero downtime, it is unrealistic to carry this with ZERO downtime. I believe Zero down is less real world but academic discussion.

                With Great Regards,
                vExpert 2012-2017 | VCP3-5 | VCAP5-DCD | VCP-NV | vSAN Specialist | VDI | Germany
                • 20. Re: NSX Edge - ECMP
                  rajeevsrikant Expert
                  Community WarriorsvExpert


                  So can you guide me what is the right steps to be followed ?

                  Sorry there were so many inputs. Not sure & not clear what are the right steps to be achieved.

                  • 21. Re: NSX Edge - ECMP
                    rajeevsrikant Expert
                    vExpertCommunity Warriors

                    I too agree that with ECMP enabled & by changing the OSPF cost it will cause unequal path & it will cause down time.

                    So what is the right sequence that needs to be followed.

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