SIP trunk and inbound calls

Hi,
i have two asterisk machines, ast1 (connected to pstn via FXO, extensions:8XX) and ast2 (extensions:1XX). between ast1 and ast2 there is a SIP trunk. the calls between 8XX and 1XX are working fine.the problem is on inbound calls in ast1:
1/ when i call from pstn, i don’t have the ability to type an 1XX extension, only the ability to type an 8XX extension
2/ when i call a pstn number from an 1XX extension, the call is not proceeded…
i am a little confused with this, any tip would be really helpful
Thanks!

Tip: provide configuration files and verbose CLI traces, if you expect useful replies.