Jul 30, 2011

--state ESTABLISHED 已建立连接--state RELATED 相关的--state INVALID 无效的. icmp 实验 通 NEW ESTABLISHED 不通 NEW ESTABLISHED RELATED INVALID 出去 iptables -t filter -A OUTPUT -p icmp -m icmp --icmp-type echo-request -m state --state NEW -j LOG --log-prefix "OUT_ICMP_NEW" Working with iptables | Network World iptables -A INPUT -m state --state NEW,ESTABLISHED,RELATED -j ACCEPT accepts packets that are part of established connections After you run iptables commands, you can use the iptables-save command iptables and Connection Tracking iptablesincludes a module that allowsadministrators to inspect and restrict connections to services availableon an internal network using a method called connectiontracking. IPTables Example Configuration - NetworkLessons.com

iptables and Connection Tracking

Jan 29, 2018 Matching connection tracking stateful - nftables wiki

Jul 19, 2013

Mar 09, 2019 · Conclusion - Checking state of NAT connection on iptables (AWS NAT instance, etc.) By using the netstat-nat command, I was able to check the status of NAT (NAPT / PAT) connections with iptables on Linux (AWS NAT instance). Jul 30, 2011 · Iptables sees all of these packets as belonging to a single connection and allows you to construct firewall rules that vary depending on the state of a given connection. Specifically, connections can be categorized as "new", "established", or "related". ESTABLISHED — The matching packet is associated with other packets in an established connection. You need to accept this state if you want to maintain a connection between a client and a server. INVALID — The matching packet cannot be tied to a known connection. The following example shows a rule that uses connection tracking to forward only the packets that are associated with an established connection: iptables -A FORWARD -m state --state ESTABLISHED,RELATED -j ACCEPT Add the state module to the INPUT chain [root@rhel01 root]# iptables -A INPUT -m state --state ESTABLISHED,RELATED -j ACCEPT The state module is used to examine the state of a packet and determine whether it is "NEW", "ESTABLISHED" or "RELATED" We can now see our two new rules so far: