4 FXO as a TRUNK

Hi,

I have Digium card with 8 FXO Ports.
I use only 4 of them and connect it to 4 FXS Port in different asterisk.
I need configure while start call with number “8” call’s route to one of this 4 ports.
Please help me configure this (trunk and route).

Thanks

Why not just trunk using IAX or SIP through the network. It would be a lot simpler.