EMP Protection of Ethernet Lines
An Cat. 5e UTP has 3 pF/m, or 300 pF / 100 m. Using this filter (like any other) you decrease the possible link budget, but this is the cost of protection. Why not? Or is it so hard for your application? Compare with 50-60 pF/m for S-STP.

Also, Ethernet has 100R at both sides in parallel, resulting in 50R equivalently. Both sides protection Tau = R*C = 50*2*30E-12=3E-9, i.e. 1/Tau is about 333.3(3) MHz, therefore it does not (significantly) limit the connection.