ASUS RT-N66U Wired Issue

Fixed 1nos of structured LAN cable done in 2 rooms. With termination of LanPort1 in Room1 and LanPort2 in Room2.

Modem, Router and PC1 is in Room1
PC2 in Room2

Modem > LanPort1 >>> LanPort2 > PC1 or PC2 600+mbps(speedtest)

Modem > Router > LanPort1 >>> LanPort2 > PC1 or PC2 90+mbps(speedtest) PROBLEM

Modem > Router > PC1 or PC2 600+mbps(speedtest)

Only 3 lan cables were used throughout the test
Modem x1
Router x1
PC1 or PC2 x1

What is it when the...

ASUS RT-N66U Wired Issue