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Nftables Nat Prerouting

Also nftables contains the concept inet that applies to all IP packets, which means one set of rules can cover both.

The one exception to inet packets in in NAT tables (like this) where ip and ipv6 need to be separate.

table ip nat { chain prerouting { type nat hook prerouting priority 0; policy accept; tcp dport 12345 dnat to 192.

168.

2.

111:ssh } }, This method uses the nftables number generator.

The example below is distributing new connections in a round-robin fashion between 192.

168.

10.

100 and 192.

168.

20.

200.

% nft add rule nat prerouting dnat to numgen inc mod 2 map { 0 : 192.

168.

10.

100, 1 : 192.

168.

20.

200 }.

The important rules regarding NAT are – not very surprising – found in the ‘ nat ‘-table.

This table has three predefinded chains: PREROUTING , OUTPUT und POSTROUTING.

The chains PREROUTING und POSTROUTING are the most important ones.

As the name implies, the PREROUTING chain is responsible for packets that just arrived at the network interface.

25/10/2019 .

The method to install nftables on a Debian/Ubuntu server is very straightforward.

In the section below, we have saved the current iptables ruleset to a.

txt file, reviewed the file, translated it to an nft readable format, and then imported it into the new nft ruleset.

25/08/2019 I installed Debian 10 Buster and Proxmox 6 on my machine and decided to use nftables instead of iptables (because future and so on).

Its a server with one public IP.

So I use NAT and masquerade.

Everything is working fine.

The Host can ping the internet and its containers.

Also the containers have internet, can ping each other and the host.

I have an OpenWRT gateway (self-built 19.

07, kernel 4.

14.

156) that sits on a public IP address in front of my private network.

I am using nftables (not iptables).

I would like to expose a non-standard port on the public address, and forward it to a standard port on a machine behind the gateway.

Basic NAT.

The following is an example of nftables rules for setting up basic Network Address Translation ( NAT ) using masquerade.

If you have a static IP, it would be slightly faster to use source nat (SNAT) instead of masquerade.

This way the router would replace the source with a predefined IP, instead of looking up the outgoing IP for every.

ID: kevin-container-web-port-http Function: nftables.

append Result: False Comment: Failed to set nftables rule for kevin-container-web-port-http.

Attempted rule was tcp dport { 80, 443 } dnat for ip.

Failed to add rule “tcp dport { 80, 443 } dnat” chain PREROUTING in table nat in family ip.

Started: 17:36:42.

821866 Duration: 154.

261 ms Changes:, # nft — add chain nat prerouting { type nat hook prerouting priority -100 ; } # nft add chain nat postrouting { type nat hook postrouting priority 100 ; } Important Even if you do not add a rule to the prerouting chain, the nftables framework requires this chain to match incoming packet replies.

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