how change the output IP of every PROXY to it's own IP in CentOS (SQUID- Multiple IP)?

i configured a proxy server in CentOS server using with squid
i have multiple ips like these :

192.233.76.1 ~ 100 

i've added those ips to my one interface.
so every HTTPS proxy works well -> ip : 443 : username : password
my problem is when i test 192.233.76.2 ~ 100 using with proxifire software the output ip is always 192.233.76.1.
i am using this site for checking output ip : http://whatismyipaddress.com/
how can i fix that problem?
i have my own vds and i have all accesses to it.(using with vmware)