Usage of fd00::/8 on the Interwebz - something with filters and uRPF

[Brian E Carpenter]

Isn't it possible for a ULA to show up in a traceroute because it's
used on an internal interface by a transit network? Your packets
may not even have crossed that interface of the router concerned.

There's also a loop between hops 6 and 7, isn't there?

But you're right, it doesn't look normal.

    Brian

On 30/05/2013 07:59, Jeroen Massar wrote:
> ...
>  4  2001:7f8:1::a500:3303:1 (2001:7f8:1::a500:3303:1)  20.755 ms  20.763 ms  20.784 ms
>  5  fd00:3303::1 (fd00:3303::1)  22.010 ms  21.984 ms  21.986 ms
>  6  2a02:120c:1051:d010::1 (2a02:120c:1051:d010::1)  17.806 ms  17.889 ms  17.842 ms
>  7  2a02:120c:1051:d010::1 (2a02:120c:1051:d010::1)  18.720 ms  18.593 ms  18.617 ms
> ...
> 
> Hmmmm fd00::/8, that really should never ever be visible on the Internet, being Unique *LOCAL* Addresses.
> And it does not look like they applied the randomness bit for picking a prefix either.
> You would also almost think that a /28 is more than enough address space to put a few router loopbacks in.
> 
> It is apparently time for people to start checking their filters again because it seems that these packets leak into other ASNs too...
> 
> More generally, do recheck your network for BCP38 compliance, please do apply it and require your peers to do the same!
> 
> Greets,
>  Jeroen
>