TMG 2010 with 2 NICs

Dear All,

I have a TMG 2010 with 2 NICs working perfectly for LAN Range 192.168.0.255 ~ 192.168.1.255. Furthermore I want to add one more range 192.168.3.0/255.255.255.0 inside Internal but that's a remote private range outside a domain connected over a lease circuit. Upon adding it, TMG authentication window appears to all clients asking for domain credantials before browsing any website since those are workgroup computers which cannot be authenticated by our domain.

I created Access Rules bypassing IP range but still the popup comes for authentication everytime, the user tries to browse internet.

I would really appreciate if could would help me?

Thanks.