I am trying plain simple authentication for squid 2.5 Stable 3.
I am not too sure how acls works in this case. I have,

acl new_test proxy_auth REQUIRE
http_access allow new_test

But where do I exactly define IP range for acl new_test?
I tried putting,
acl new_test src
But I am getting the error,
aclParseAclLine: ACL 'new_test' already exists with different type,

What is wrong exactly? Where do I put the IP range for authentication.
My next step would be to use smb authentication after this basic thing
starts working.
I also happen to have,
auth_param basic program /usr/lib/squid/ncsa_auth /etc/squid/htpasswd