Routing

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

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

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

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

Alex, thanks for the detailed answer.

     Eyal