We describe Prex, a tool for analyzing MPLS networks leveraging an
automata theoretic approach. While we base our approach on previous
works, we extend their approaches in a multitude of ways. We introduce a
method of constructing queries based on regular expressions which permits
the user to write highly complex queries, and implement a method of
verifying these queries on the networks. We benchmark our tool and
compare it with another recognized tool. We perform a case study on a
large scale in production MPLS network, and use our tool verify certain
interesting properties in their network.