# FreeBSD 10 RA (rtadvd) issues



## gizah123 (Jan 22, 2014)

I seem to be having some issues to get rtadvd() working. 

From my ISP I get a /64 range using 6rd, I'm using the userland tool u6rd to get it working on a tun interface: xxxx:xxxx:xxxx::4d00::1.
On my internal interface I've set up a /65 adress xxxx:xxxx:xxxx:4d00:8000::2, routing works from my inside network as long as I use a static config.

For some reason rtadvd is not setting my clients up using auto configuration (both Windows and Linux machines). My /65 route _does_ get pushed, but it's just the address auto configuration that somehow fails.  If I change my internal interface to an /64 and push my /64 range auto configuration is successful (but obviously clients can't reach the external interface on the router this way). 

rtadvd.conf

```
re0:\
   :addr="xxxx:xxxx:xxxx:4d00:8000::":prefixlen#65:
```

Anybody able to tell me where things go wrong?


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## junovitch@ (Jan 22, 2014)

You can only use 64 bit prefixes for stateless auto-configuration.  I'm not sure what RFC that's in but here's some good Cisco reference on it: http://www.cisco.com/web/about/ac123/ac147/archived_issues/ipj_7-2/ipv6_autoconfig.html.


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## gizah123 (Jan 22, 2014)

Thanks  I actually also just found out  And found out that my ISP did delegate an /56 to me.

There seem to be a few bad ISPs that do just delegate an /64, luckily mine is not one of them


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