how to configure squid

[ning luwen]

Hi,
I have a problem set up squid. described as follow:

the squid server ip for example ,a.b.c.d,
after setup , the ips like a.b.c.e can use the http proxy normally,
but ips like f.g.h.i just can not use the proxy.

additional information:
Two machine can ping each other.

my Ubuntu distribution is 10.04(both squid server and client),
and squid configure file is simple change deny all to allow all.

any suggestion?

regards,
ningluwen