Squid inside firewall

My local network is behind a firewall.
There are two proxy servers outside firewall and these
are only servers which have direct internet connection.
All hosts inside firewall are have no internet connection.

I try to build a proxy server inside firewall with squid-2.2PRE2.

Squid-1.1 has inside_firewall directive in squid.conf to
specify a list of domains internal to my firewall.
But Squid-2.1 or higher replaced it with never_direct to my despair.

With following squid.conf
        cache_host proxy1.parent.domain.com parent 8080 3130 round-robin
        cache_host proxy2.parent.domain.com parent 8080 3130 round-robin
        inside_firewall mydomain.parent.domain.com
where proxy[12].parent.domain.com is external proxy with Netscape-Proxy/2.5,
my internal proxy always fetch objects from proxy1 or proxy2.

But with folowing squid.conf,
        cache_peer proxy1.parent.domain.com parent 8080 3130 round-robin
        cache_peer proxy2.parent.domain.com parent 8080 3130 round-robin
        never_direct mydomain.parent.domain.com
my internal proxy never fetch objects from proxy1 or proxy2.

How to make squid always fetch objects from proxy1 or proxy2 which have
internet connection?

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