request for help in finding a blackhole

[Jogi Hofmüller]

Hi Drake, all

On Wed, May 05, 2010 at 12:35:09AM -0500, Drake Wilson wrote:
> Quoth "Frank Bulk - iName.com" <frnkblk at iname.com>, on 2010-05-04 13:11:22 -0500:
> > What does mturoute show?
> 
> After receiving clarifications (thanks), installed tracepath6.
> tracepath6 www.mur.at from drache.begriffli.ch:
> 
>  1?: [LOCALHOST]                      pmtu 1500
>  1:  zwischenschaltung.begriffli.ch             0.946ms
>  1:  zwischenschaltung.begriffli.ch             0.999ms
>  2:  zwischenschaltung.begriffli.ch             0.929ms pmtu 1472
>  2:  begrifflich.tunnel.tserv8.dal1.ipv6.he.net  44.573ms
>  2:  begrifflich.tunnel.tserv8.dal1.ipv6.he.net  44.608ms
>  3:  gige-g2-14.core1.dal1.ipv6.he.net         43.319ms
>  4:  10gigabitethernet1-4.core1.chi1.he.net    70.560ms
>  5:  ibx-chi.ip6.tiscali.net                   69.641ms asymm  6
>  6:  xe-2-1-0.nyc20.ip6.tinet.net              87.755ms asymm  8
>  7:  xe-5-2-0.lon11.ip6.tinet.net             212.686ms asymm  9
>  8:  xe-9-2-0.lon10.ip6.tinet.net             165.985ms
> [... "no reply" thereafter]
> 
> Using the -l option to set initial packet size and doing a
> quasi-binary search yields the same results down to -l 1450, at
> which point more hops come into view:
>  
>  9:  no reply
> 10:  no reply
> 11:  Aconet.tu-637.sar1.Amsterdam1.Level3.net 233.160ms asymm 12
> 12:  2001:628::a089:0:1                       239.639ms asymm 13
> [... "no reply" thereafter]

After hop 12 (our border router) there is only our webserver which does
not reply to UDP pakets.  You can use birke.mur.at as an alternative
traceroute6/ping6 target since this host is less restrictive than our
webserver.  Unfortunately tracepath6 does not provide the possibility of
using ICMP pakets for its probes (like traceoute's -I flag).

> which matches the earlier ICMPv6 echo traceroute up to the last hop
> before the final destination.
> 
> Does this suggest an MTU breakage near that point?

Quite frankly I have no idea :(  I can state with almost 100% certainty
that it's not anywhere near us since we would be expecting a lot more
troubles using IPv6, which we don't.

Thanks so far!

Cheers,
j.
-- 
j.hofmüller                                http://users.mur.at/thesix/
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