PPOE TAKES A DEFAULT GATEWAY 128.0.0.1 CONTRARY TO MY ISP GATEWAY IP

 We are using Cyberoam 50ing. I am having a challenge in configuring my PPOE link.Every time i configure the ppoe link it automatically picks a default gateway (128.0.0.1) which is not the isp gateway ip as it appears in my cyberoam.This problem does not allow me to finalize the ppoe configuration since it never connects.Kindly advise on how to go about this issue.