I'm setting up and testing IPv6 on our network and have run into a snag with our windows clients.. 

I've got a Cisco Catalyst 3850 switch setup for ipv6 unicast-routing and have two networks setup on it. The catalyst switch also has a working ipv6 route out to the internet and I've been able to successfully contact public ipv6 server addresses without issue from the switch CLI (from the switch's ipv6 gateway address on either network).

The gateway addresses/networks on the switch are:
VLAN 20: 2607:f460:21c0:a020::1/64
VLAN 200: 2607:f460:21c0:a200::1/64

I can ping one of the configured networks from the other with no issue:

```
ping 2607:f460:21c0:a200::1 source 2607:f460:21c0:a020::1
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 2607:F460:21C0:A200::1, timeout is 2 seconds:
Packet sent with a source address of 2607:F460:21C0:A020::1
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 1/2/10 ms

```

There are no ACLs or special routes setup on the switch other than the default ::/0 public route to the internet.

The windows client resides on VLAN 20 and has the static address:
2607:f460:21c0:a020::2/64 with 2607:f460:21c0:a020::1 set as the default gateway..

If I ping the gateway, it works...

```
C:\Windows\system32>ping 2607:f460:21c0:a020::1

Pinging 2607:f460:21c0:a020::1 with 32 bytes of data:
Reply from 2607:f460:21c0:a020::1: time=2ms
Reply from 2607:f460:21c0:a020::1: time=2ms
Reply from 2607:f460:21c0:a020::1: time=2ms

C:\Windows\system32>tracert -6 2607:f460:21c0:a020::1

Tracing route to 2607:f460:21c0:a020::1 over a maximum of 30 hops

  1     2 ms     2 ms     2 ms  2607:f460:21c0:a020::1

Trace complete.

```

If I try to ping anything outside the local On-Link network, it fails with an unreachable error:

```
C:\Windows\system32>ping 2607:f460:21c0:a200::1

Pinging 2607:f460:21c0:a200::1 with 32 bytes of data:
Destination host unreachable.
Destination host unreachable.
Destination host unreachable.
Destination host unreachable.

Ping statistics for 2607:f460:21c0:a200::1:
    Packets: Sent = 4, Received = 0, Lost = 4 (100% loss),

Tracing route to 2607:f460:21c0:a200::1 over a maximum of 30 hops

  1  Destination host unreachable.

Trace complete.

```

The fact that the trace fails on the first hop with unreachable implies to me that windows does not seem to be trying to contact the default route but rather is searching for the host on-link...

This doesn't make sense to me, because I have a gateway set, and it has a lower metric than the on-link route..

```
===========================================================================
Interface List
  7...00 50 56 94 e7 38 ......vmxnet3 Ethernet Adapter
  1...........................Software Loopback Interface 1
===========================================================================

IPv6 Route Table
===========================================================================
Active Routes:
 If Metric Network Destination      Gateway
  7    271 ::/0                     On-link
  7    271 ::/0                     fe80::521c:bfff:fe73:1656
  7     16 ::/0                     2607:f460:21c0:a020::1
  1    331 ::1/128                  On-link
  7    271 2607:f460:21c0:a020::/64 On-link
  7    271 2607:f460:21c0:a020:947a:1291:c6e3:b93d/128
                                    On-link
  7    271 fd67:df27:a77::/48       On-link
  7    271 fd67:df27:a77:7777::/96  On-link
  7    271 fe80::/64                On-link
  7    271 fe80::947a:1291:c6e3:b93d/128
                                    On-link
  1    331 ff00::/8                 On-link
  7    271 ff00::/8                 On-link
===========================================================================
Persistent Routes:
  None

```

Anyone able to help me with this?