[asgolden]

В Squid 2.6 изменились опции конфига :
# You may specify multiple socket addresses on multiple lines.
#
# options are:
# transparent Support for transparent proxies
# vhost Accelerator using Host directive
# vport Accelerator with IP virtual host support
# vport= As above, but uses specified port number
# rather than the http_port number.
# defaultsite= Main web site name for accelerators.
# urlgroup= Default urlgroup to mark requests
# with (see also acl urlgroup and
# url_rewrite_program)
# protocol= Protocol to reconstruct accelerated
# requests with. Defaults to http.
# no-connection-auth
# Prevent forwarding of Microsoft
# connection oriented authentication
# (NTLM, Negotiate and Kerberos)
# tproxy Support Linux TPROXY for spoofing
# outgoing connections using the client
# IP address.
#
# If you run Squid on a dual-homed machine with an internal
# and an external interface we recommend you to specify the
# internal address:port in http_port. This way Squid will only be
# visible on the internal address.
#

Например http_port 192.168.0.1:3128 transparent - для прозрачного проксирования,
естественно надо перенаправить на порт 3128 все возможные порты в Iptables.