6to4 strangeness

Bernhard Schmidt berni at birkenwald.de
Tue Feb 14 23:35:44 CET 2006

Bernhard Schmidt wrote:

>>> This means that for them, or rather, their 6to4 gateway, my  
>>> 2001:1af8::/32 address is unreachable, but 3ffe:2500::/32 works. WTF?
>> Whois shows the IPv4 address belongs to HopOne
>> Internet. They have a traceroute server which I used to traceroute
>> to It looks like the route currently leads to
>> teleport-iabg.de. Is there anyone from there on this list who could
>> check their route back to 2001:1af8::/32?
> Great, that is one of mine, once across the galaxy^Watlantic ocean. I 
> can reach Iljitsch just fine though:

Something else is odd here, too. The box the 6to4 relay is running on 
has IOS 12.4(5) and does Netflow v9 export to the current nfdump/nfsen 
beta (_very_ nice tool btw). I see tons of flows with source 2002::/16 
and ingress interface = 6to4 tunnel (almost 40k flows today between 6am 
and 11pm), but only one flow with 2002:42EB:B46B::2 ... as destination 
address when I tested it from my box here.

My guess is that they don't use the anycast address (maybe because it 
gets routed to Europe) but a hardcoded relay. Which is broken. Nothing 
more to say without a trace from their side.


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