show ipv6 destination cache on BSD host

[Matjaz Straus Istenic]

On 30. jan. 2014, at 21:13, Nick Hilliard <nick at inex.ie> wrote:

> ndp -an
Well, this is for local IPv6 ND cache only. I'm looking for a command to display the _destination_ cache in order to check for changed Path MTU. Rui's suggestions works fine:

# in this example 2001:xxxx:e813:a00::d25 is behind a link with MTU of 1400 bytes:
root at FreeBSD:~ # ping6 -m -s 5000 2001:xxxx:e813:a00::d25
PING6(5048=40+8+5000 bytes) 2001:xxxx:e811:b00:20c:29ff:fe78:31fb --> 2001:xxxx:e813:a00::d25
5008 bytes from 2001:xxxx:e813:a00::d25, icmp_seq=0 hlim=63 time=1.088 ms
5008 bytes from 2001:xxxx:e813:a00::d25, icmp_seq=1 hlim=63 time=0.903 ms
5008 bytes from 2001:xxxx:e813:a00::d25, icmp_seq=2 hlim=63 time=0.985 ms
^C
--- 2001:xxxx:e813:a00::d25 ping6 statistics ---
3 packets transmitted, 3 packets received, 0.0% packet loss
round-trip min/avg/max/std-dev = 0.903/0.992/1.088/0.076 ms

root at FreeBSD:~ # sysctl -o net.inet.tcp.hostcache.list
net.inet.tcp.hostcache.list:
IP address        MTU  SSTRESH      RTT   RTTVAR BANDWIDTH     CWND SENDPIPE RECVPIPE HITS  UPD  EXP
2001:xxxx:e813:a00::d25  1400        0      0ms      0ms         0        0        0        0   11    1 3600
                        ^^^^^^

> 
> ?
> 
> Sent from my iWotsit.
> 
>> On 30 Jan 2014, at 18:12, Matjaz Straus Istenic <matjaz at njetwork.si> wrote:
>> 
>> Hi list!
>> 
>> I'm struggling to find a way to display IPv6 destination cache on a FreeBSD or UNIX (not Linux) system. 
>> 
>> This is the way on Linux:
>> ip -6 route get <address>
>> 
>> Mac OS X:
>> netstat -f inet6 -narlW
>> 
>> ...and Windows:
>> netsh interface ipv6 show destinationcache
>> 
>> ...but on FreeBSD (I've tried with 9 and 10), netstat -narlW does not show any entries despite the local routes. On OS X option -a does the trick, but on FreeBSD I see no difference in output with or without -a.
>> 
>> Is there any other option for a BSD machine to figure out the Path MTU value for a certain IPv6 destination? OK, except tcpdump, of course ;-).
>> 
>> Any hint is appreciated!
>> Thanks!
>> 
>> Kind regards,
>>   Matjaž

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