Issues with vias on ethernet differential signals in routing

[FreshmanNewbie]

I have ethernet differential signals and a discrete magnetics part.

I want to know what issues might arise if I place vias on the differential signals when connecting them between the magnetics and the ethernet PHY?

Can someone explain in simple terms?

 

[FvM]

In simple terms, vias on fast signals (differential as well as single ended) are feasible but should be minimized.

 

[barry]

In even simpler terms, vias might corrupt your signals or they may not.