Assalam-o-Alikum

I have :-

1. Worldcall Motorola Cable Modem ( surfboard 5101)
2. Ptcl An1020 Adsl modem (not in use)
3. Airport Express Wifi Router


I have worldcall internet. i want use ptcl modem as a router and connect my apple wifi from ptcl router.

I connected ptcl router with worldcall router. but when i connect my pc and my wifi with ptcl router aik jagah chalta hai dosri jagah nahi chalta..

Please help