request for help in finding a blackhole

[sthaug at nethelp.no]

> 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]
> 
> 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?

Confirmed. I get a "packet too big" ICMPv6 message from the Level3
router:

08:07:49.873715 IP6 2001:1900:5:1::1d > 2001:8c0:9200:1::2: ICMP6, packet too big, mtu 1450, length 1240

Steinar Haug, Nethelp consulting, sthaug at nethelp.no