OpenBSD does not always play well with our current IPv6 networking setup. The following link provides more information: http://openbsd-archive.7691.n7.nabble.com/OpenBSD-ignoring-RFC-compliant-IPv6-neighbor-solicitation-td223348.html

OpenBSD has non-RFC compliant hardening that needs to be removed in order to allow your VPS to accept the RFC compliant response from our router. The text of the patch from that link is included below:

--------
Index: nd6_nbr.c
===================================================================
RCS file: /cvs/src/sys/netinet6/nd6_nbr.c,v
retrieving revision 1.66
diff -u -p -r1.66 nd6_nbr.c
--- nd6_nbr.c   7 Mar 2013 09:03:16 -0000   1.66
+++ nd6_nbr.c   7 May 2013 11:44:56 -0000
@@ -132,17 +132,7 @@ nd6_ns_input(struct mbuf *m, int off, in
       "(wrong ip6 dst)\n"));
    goto bad;
    }
-   } else {
-   /*
-   * Make sure the source address is from a neighbor's address.
-   */
-   if (!in6_ifpprefix(ifp, &saddr6)) {
-   nd6log((LOG_INFO, "nd6_ns_input: "
-      "NS packet from non-neighbor\n"));
-   goto bad;
-   }
    }
-

    if (IN6_IS_ADDR_MULTICAST(&taddr6)) {
    nd6log((LOG_INFO, "nd6_ns_input: bad NS target (multicast)\n"));
--------

As a work around, you can try setting the prefixlen to 40 from 48. The only down side to that is if you try to reach another server from within our network via IPv6, it may not respond.

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