During the test of ipv6 nat66 (NPT), a problem was discovered, that is, the prefix conversion is expected behavior, but the upstream cannot reply from its interface. The root cause is that vyos cannot respond to the NDP query request of the translated prefix. To support stateless NAT66 (NPT), it is necessary to support NDP proxy function.
The ndp proxy relies on the `ndppd` package to achieve
Nptv6 of Vyos 1.2 has the same problem
Here are some examples
```
set protocol ndp-proxy interfaces <interface> rules <ipv6-prefix> mode auto
```
or
```
set protocol ndp-proxy interfaces <interface> rules <ipv6-prefix> mode static
```
or
```
set protocol ndp-proxy interfaces <interface> rules <ipv6-prefix> mode iface
set protocol ndp-proxy interfaces <interface> rules <ipv6-prefix> outbound-interface <interface>
```
Reference: [1] [[ https://www.spinics.net/lists/netfilter/msg53833.html | Re: How to use IPv6 SNPT? ]]