sysctl -w net.ipv4.ip_forward=1

iptables -t nat -A PREROUTING -i eth0 -s 192.168.1.19 -p TCP -j DNAT --to-destination irc.something.net:6667
iptables -t nat -A POSTROUTING -o eth0 -j SNAT  --to-source 192.168.48.128

iptables -t nat -A PREROUTING -i eth0 -s irc.something.net:6667 -p TCP -j DNAT --to-destination 192.168.1.19
iptables -t nat -A POSTROUTING -o eth0 -j SNAT --to-source 192.168.48.128

iptables -A FORWARD -i eth0 -o eth0 -j ACCEPT