ipv6 problem

Thomas Sandford freebsduser at paradisegreen.co.uk
Thu Feb 3 16:10:23 UTC 2011

On 01/02/2011 07:29, pepe wrote:
> I have 2001:14b8:10:402::/64 ipv6 from my isp and I cant get it working.
> Ifconfig should be ok:
> backup# ifconfig rl0 inet6
> rl0: flags=8843<UP,BROADCAST,RUNNING,SIMPLEX,MULTICAST>  metric 0 mtu 1500
>          options=8<VLAN_MTU>
>          inet6 2001:14b8:10:402:2::1 prefixlen 64

Looks a bit odd - I would expect to see a link-local address too - eg

%ifconfig bge0 inet6
bge0: flags=8843<UP,BROADCAST,RUNNING,SIMPLEX,MULTICAST> metric 0 mtu 1500
         inet6 fe80::20b:cdff:fef2:9a57%bge0 prefixlen 64 scopeid 0x1
         inet6 2001:8b0:cae3:1:20b:cdff:fef2:9a57 prefixlen 64 autoconf

> default gateway is set to 2001:14b8:10:402:1::1.

That sounds a slightly odd comment, since in general IPv6 routing is 
done with auto-discovery. Especially given the fact that the default 
route quoted lies within the same subnet (2001:14b8:10:402:: prefixlen 
64) as the host in question.

  When I try to traceroute
> irc server for example
> I get this:
> traceroute6: Warning: irc.cc.tut.fi has multiple addresses; using
> 2001:708:310:4952:4320:5365:7276:6572

I get this message too - because the host irc.cc.tut.fi DOES have 
multiple addresses:

%dig irc.cc.tut.fi aaaa

; <<>> DiG 9.6.2-P2 <<>> irc.cc.tut.fi aaaa
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 24710
;; flags: qr rd ra; QUERY: 1, ANSWER: 2, AUTHORITY: 3, ADDITIONAL: 0

;irc.cc.tut.fi.                 IN      AAAA

irc.cc.tut.fi.          3134    IN      AAAA 
irc.cc.tut.fi.          3134    IN      AAAA 

cc.tut.fi.              172334  IN      NS      ns-secondary.funet.fi.
cc.tut.fi.              172334  IN      NS      kaustinen.cc.tut.fi.
cc.tut.fi.              172334  IN      NS      ressu.cc.tut.fi.

;; Query time: 0 msec
;; WHEN: Thu Feb  3 15:34:06 2011
;; MSG SIZE  rcvd: 164

> traceroute6 to irc.cc.tut.fi (2001:708:310:4952:4320:5365:7276:6572) from
> 2001:14b8:10:402:2::1, 64 hops max, 12 byte packets
>   1  2001:14b8:10:402:2::1  2026.908 ms !A  2999.587 ms !A  3000.423 ms !A

 From the traceroute6 manpage
!A      Destination Unreachable - Address Unreachable.

It also appears that your first hop address is the same as your source 
address, which does suggest that routing is more than a little bit screwy.

On my system I get:

%traceroute6 -n irc.cc.tut.fi
traceroute6: Warning: irc.cc.tut.fi has multiple addresses; using 
traceroute6 to irc.cc.tut.fi (2001:708:310:4952:4320:436c:6965:6e74) 
from 2001:8b0:cae3:1:20b:cdff:fef2:9a57, 64 hops max, 12 byte packets
  1  2001:8b0:cae3:1:21a:a2ff:fe34:e50b  1.349 ms  0.969 ms  1.011 ms
  2  2001:8b0:0:53:203:97ff:fe05:8000  129.118 ms  143.449 ms  119.622 ms
  3  2001:7f8:4::50e8:1  132.075 ms  119.009 ms  117.983 ms
  4  2001:7f8:4::1b1b:1  123.832 ms  114.424 ms  119.675 ms
  5  2001:7f8:4::a2b:1  114.905 ms  119.009 ms  118.030 ms
  6  2001:948:1:8::3  134.205 ms  143.579 ms  130.875 ms
  7  2001:948:1:2::3  145.068 ms  145.049 ms  156.321 ms
  8  2001:948:3:2::3  165.258 ms  171.228 ms  156.591 ms
  9  2001:708:0:f000:0:60:3060:2  233.114 ms  163.319 ms  158.668 ms
10  2001:708:310::2  67.252 ms  58.513 ms  59.656 ms
11  2001:708:310:4952:4320:436c:6965:6e74  58.906 ms  58.310 ms  58.045 ms

(I ran it with -n as I think in this case the raw IPv6 addresses are 
more informative than the rDNS lookups).

> So. Could this be problem in my configs or is this because of something
> wrong at the isp side?

It does look as though there is something a little odd with your 
configs. It's difficult to be more specific because you've given very 
little information.

If things at the router (whether yours or at the isp) are set up 
correctly then the single line in /etc/rc.conf


should be sufficient to autoconfigure BOTH ipv6 address and routing 
using Router Discovery. This is all that I had to do on the machine I 
generated the above config dumps & traces from.

In my case my ISP (AAISP in the UK) have allocated me a /48 2001:8b0:cae3::

Traffic comes to me over a 6to4 tunnel from the ISP terminated on a 
Cisco router (though I tested it on a FreeBSD host before I got the 6to4 
tunnel set up on the router). The LAN side interface of the router has 
Router Advertisements enabled which means that the above rc.conf line is 
all that is required for everything to "just work".

Thomas Sandford

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