Multiple NATs using nftables maps

Thanks to nftables Maps, if you have a previous iptables NAT (destination NAT) ruleset like this:

% iptables -t nat -A PREROUTING -p tcp --dport 1000 -j DNAT --to-destination 1.1.1.1:1234
% iptables -t nat -A PREROUTING -p udp --dport 2000 -j DNAT --to-destination 2.2.2.2:2345
% iptables -t nat -A PREROUTING -p tcp --dport 3000 -j DNAT --to-destination 3.3.3.3:3456

It can be easily translated to nftables in a single line:

% nft add rule nat prerouting dnat to \
      tcp dport map { 1000 : 1.1.1.1, 2000 : 2.2.2.2, 3000 : 3.3.3.3} \
      : tcp dport map { 1000 : 1234, 2000 : 2345, 3000 : 3456 }

Likewise, in iptables NAT (source NAT):

% iptables -t nat -A POSTROUTING -s 192.168.1.1 -j SNAT --to-source 1.1.1.1
% iptables -t nat -A POSTROUTING -s 192.168.2.2 -j SNAT --to-source 2.2.2.2
% iptables -t nat -A POSTROUTING -s 192.168.3.3 -j SNAT --to-source 3.3.3.3

Translated to a nftables one-liner:

% nft add rule nat postrouting snat to \
      ip saddr map { 192.168.1.1 : 1.1.1.1, 192.168.2.2 : 2.2.2.2, 192.168.3.3 : 3.3.3.3 }

Multiple NAT mapping with address and port

You might also need to define a NAT mapping that includes the IP address and port, such as:

% nft add map nat foo { type inet_service : ipv4_addr . inet_service ; }
% nft add element nat foo { \
    1100 : 192.168.1.2 . 5061, \
    1101 : 192.168.1.3 . 5061, \
    1400 : 192.168.1.4 . 5061 \
}
% nft add rule nat pre ip protocol udp dnat ip addr . port to udp dport map @foo

If your mapping does not need to be updated, you could use a anonymous map in your rule instead:

% nft add rule nat pre ip protocol udp dnat ip addr . port to udp dport map { 1100 : 192.168.1.2 . 5061, 1101 : 192.168.1.3 . 5061, 1400 : 192.168.1.4 . 5061 }

See also

• Performing NAT with nftables