Facebook & Traceroute

[lists.nanog at monmotha.net (Brandon Martin)]

On 03/09/2016 10:53 PM, Sam Norris wrote:
> Why does Facebook spoof the source IP address of the hop before this server?
> They spoof the source IP address that is performing the traceroute.
...
> (31.13.28.207)  67.846 ms ae12.dr08.ash3.tfbnw.net (31.13.29.191)  68.629 ms
> 12  * * *
> 13  * * *
> 14  8.25.38.1 (8.25.38.1)  68.571 ms  68.718 ms  68.132 ms
> 15  edge-star-mini-shv-07-ash4.facebook.com (66.220.156.68)  67.903 ms  67.752
> ms  68.071 ms
> ---
>
> Hop 14 is the source ip of the traceroute which is forged. This essentially
> makes hop 14 reply using the same ip for src and dst.

If intentional, I would speculate that this might be something to help 
their support staff by giving them confirmation of where the traceroute 
actually originated from in the public Internet view given that the 
originator might actually be behind possibly several layers of NAT.  The 
two missing hops could be a marker or perhaps other info that got eaten 
due to various source filters?

-- 
Brandon Martin