Source Address Translation has been implemented in two different ways in iptables, as SNAT and as MASQUERADE. The difference is that the MASQUERADE target extension is intended for use with connections on interfaces with dynamically assigned IP addresses, particularly in the case in which the connection is temporary and the IP address

iptables is a command line interface used to set up and maintain tables for the Netfilter firewall for IPv4, included in the Linux kernel. The firewall matches packets with rules defined in these tables and then takes the specified action on a possible match. Tables is the name for a set of chains.; Chain is a collection of rules.; Rule is condition used to match packet. How can I setup NAT on my OpenVPN Server for the client Jul 22, 2020 [NETWORK] Routing with MASQUERADE from vm lans to wan Hello Fellow proxmoxers, I've been using this VE for a while now, and I have to say I have been pretty pleased with it through the years. Alas, now I am facing a weird issue that I cannot seem to find the solution of. CURRENT /etc/network/interface OF PVE auto lo iface lo inet loopback iface iptables -t nat -A POSTROUTING -o ppp0 -j MASQUERADE The “liberal” form is better for temporary connections: MASQUERADE automatically chooses address The -j MASQUERADE target is specified to mask the private IP address of a node with the external IP address of the firewall/gateway. If you have a server on your internal network that you want make available externally, you can use the -j DNAT target of the PREROUTING chain in NAT to specify a destination IP address and port where incoming

iptables is a pure packet filter when using the default 'filter' table, with optional extension modules. This should simplify much of the previous confusion over the combination of IP masquerading and packet filtering seen previously.

Aug 29, 2017 Linux Network Administrator's Guide, 2nd Edition: Chapter

iptables -t nat -A POSTROUTING -s -o eth0 -j MASQUERADE. If your default iptables OUTPUT value is not ACCEPT, you will also need a line like: iptables -A OUTPUT -o tun+ -j ACCEPT. That's it now restart the iptables service and you are finished.

# /sbin/iptables -t nat -A POSTROUTING -o eth0 -j MASQUERADE # /sbin/iptables -A FORWARD -i eth0 -o eth1 -m state --state RELATED,ESTABLISHED -j ACCEPT # /sbin/iptables -A FORWARD -i eth1 -o eth0 -j ACCEPT You should now be NATing. You can test this by pinging an external address from one of your internal hosts. MASQUERADE is an iptables target that can be used instead of SNAT target (source NAT) when external ip of the inet interface is not known at the moment of writing the rule (when server gets external ip dynamically). Feb 20, 2020 · # iptables -t nat -A POSTROUTING ! -d -o eth1 -j MASQUERADE However, please note that, for static IPs, SNAT is suggested as from the iptables man page : > This target is only valid in the nat table, in the POSTROUTING chain. Aug 29, 2017 · iptables-A INPUT -p tcp -m multiport --dports 22,5901 -s -j DROP. Let us consider another example. Say, you want to block ICMP address mask requests (type 17). First, you should match ICMP traffic, and then you should match the traffic type by using icmp-type in the icmp module: iptables-A INPUT -p icmp -m icmp --icmp-type 17 -j DROP iptables -t nat -I POSTROUTING -s -o eth0 -j MASQUERADE (I have put this line in iptables-persistent file and load iptables-restore in /etc/rc.local). I have read on other forums regarding similar issues that it is quite normal to enable masquerading when using OpenVPN.