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using IPv6 anycast ip address instead of vrrp

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  • 1.  using IPv6 anycast ip address instead of vrrp

    Posted 07-06-2020 23:00

    Hello,

     

      I was wandering if I can use the optin of IPv6 anycast address instead of configuring IPv6 vrrp.

      I have the following topology (see the topology below) and I don't want to use any dynamic routing protocol,

      and I prefer not to config IPv6 vrrp.

      R1 and R2 should be the default gateway of R3

      On R3, can I use anycast address of xxx::0 as the default gateway,

      meaning can I config "set routing-options rib inet6.0 static route ::/0 next-hop xxx::0"  and will it work ?

     

      Thanks,

     

            Eyal

     

     

     

     

      

    vrrp.jpg

     



  • 2.  RE: using IPv6 anycast ip address instead of vrrp

     
    Posted 07-07-2020 13:52

    Hi eyalb@ccc.co.il

     

    Greetings, In order for this to work you will need to add the following knob on both routers.

    subnet-router-anycast

    Example:

    set interfaces [interface name.unit] family inet6 address xxx:1/xx subnet-router-anycast

     

    If this solves your problem, please mark this post as "Accepted Solution" so we can help others too \:)/

    Regards,

    Lil Dexx
    JNCIE-ENT#863, 3X JNCIP-[SP-ENT-DC], 4X JNCIA [cloud-DevOps-Junos-Design], Champions Ingenius, SSYB



  • 3.  RE: using IPv6 anycast ip address instead of vrrp

    Posted 07-08-2020 08:37

    Hi,

     

      I have tried the configuration.

      It works only when both interface in R1 and R2 are up.

      When one of interfaces in R1 or R2 is down the connectivity is lost.

      R1 interface configuration:

      set interfaces ae1 unit 146 family inet6 address xxx:1::3/125 subnet-router-anycast

      R2 interface configuration:

      set interfaces ae1 unit 146 family inet6 address xxx:1::2/125 subnet-router-anycast

      On R3 I set the default route to: xxx:1::0

      For example: I pinged from R3 to google ipv6 dns: 2001:4860:4860::8888

      While both interface were up it worked fine.

      once I closed one of the interfaces on R1 or R2 the pings dropped.

      my purpose was that the anycast will replace the vrrp whwn one of the interface is going down.

     

       Is there a way to use anycast ipv6 address instead of ipv6 vrrp ?

     

          Thanks

     

              Eyal



  • 4.  RE: using IPv6 anycast ip address instead of vrrp

    Posted 07-08-2020 11:02

    Hello,

     


    eyalb@ccc.co.il wrote:

     

       Is there a way to use anycast ipv6 address instead of ipv6 vrrp ?

     

       

     

    Theoretically yes.

    Practically - not so much.

    Please check out this page https://nextheader.net/2017/04/18/subnet-router-anycast-address-on-junos/

    It makes clear that Your R3 must do Neighbor (re)discovery when its previous default gateway silently becomes unreachable, and this ND can be only periodic - there is no trigger event on R3 to re-do ND when R1 or R2 silenly drop off from the central switch.

    VRRP uses predictable VMAC , hence backup router and master router independently calculate and use the same VMAC to reply to ARPs/NDs from hosts, and VRRP VMAC does not change when VRRP mastership switches over.

    HTH

    Thx

    Alex

     



  • 5.  RE: using IPv6 anycast ip address instead of vrrp
    Best Answer

    Posted 07-09-2020 04:05

    Alex, thanks for the detailed answer.

     

         Eyal