Traces should be routed with 50-Ω impedance to ground and 100-Ω differential controlled impedance
Route MDI traces to the transformer on the same layer
Use a metal shielded RJ-45 connector and electrically connect the shield to chassis ground
Avoid supplies and ground beneath the magnetics
Do not overlap the circuit ground and chassis ground planes. Keep chassis ground and circuit ground isolated by turning chassis ground into an isolated island by leaving a gap between the planes. Connecting a 1206 (size) capacitor between chassis ground and circuit ground is recommended to avoid floating metal. Capacitors less than 805 (size) can create an arching path for ESD due to a small air-gap.