squid proxy gateway based downloaded object

#  TAG: tcp_outgoing_address
#       Allows you to map requests to different outgoing IP addresses
#       based on the username or sourceaddress of the user making
#       the request.
#
#       tcp_outgoing_address ipaddr [[!]aclname] ...
#
#       Example where requests from 10.0.0.0/24 will be forwareded
#       with source address 10.1.0.1, 10.0.2.0/24 forwarded with
#       source address 10.1.0.2 and the rest will be forwarded with
#       source address 10.1.0.3.
#
#       acl normal_service_net src 10.0.0.0/255.255.255.0
#       acl good_service_net src 10.0.1.0/255.255.255.0
#       tcp_outgoing_address 10.0.0.1 normal_service_net
#       tcp_outgoing_address 10.0.0.2 good_service_net
#       tcp_outgoing_address 10.0.0.3 

Reference here