Router cutting WIRED speeds in half

[ccollins76]

Linksys e2500, wired download speeds tested several times go from 100Mbps (on modem alone), to about 50Mbps (with router).

Have already tried:
Different ethernet cables, different speed tests, factory resetting router, firmware updating router, disablling QoS on router, and different MTU sizes, ports are showing as 10/100 as well.

Anyone have any other ideas?

 

[rgd1101]

and the exact model of the modem and router?

 

[ccollins76]

and the exact model of the modem and router?

Modem: Netgear cm400

Router: Linksys E2500 v1