Everybody is good, use centos iptables do user limit (NAT), restrict the URL of the user to access the network, and limit the use of some APP (via IP), current testing are some of the URL to access allows slow (including IP), and even can't access, (see the iptables rules can see package flow, effective rules). Could you tell me where is the reason, don't iptables is suitable for the user to access restrictions? Passing a friend, please give some advice, advice, thank you very much,