  IP spoofing enables reflection and amplification attacks, which cause major
threats to the current Internet infrastructure. Detecting IP packets with
incorrect source addresses would help to improve the situation. This is easy at
the attacker's network, but very challenging at Internet eXchange Points (IXPs)
or in transit networks. In this reproducibility study, we revisit the paper
\textit{Detection, Classification, and Analysis of Inter-Domain Traffic with
Spoofed Source IP Addresses} published at ACM IMC 2017. Using data from a
different IXP and from a different time, we were not able to reproduce the
results. Unfortunately, our further analysis reveals structural problems of the
state of the art methodology, which are not easy to overcome.
