прямо из squid.conf:
# acl aclname src      ip-address/netmask ... (clients IP address)
# acl aclname src      addr1-addr2/netmask ... (range of addresses)

acl mynet src 192.168.2.2-192.168.2.7/32
acl mynet src 192.168.2.58-192.168.2.60/32
acl mynet src 192.168.2.101/32

acl secondnet src 192.168.3.0/29
acl secondnet src 192.168.3.224/29