Iptables redirect port

iptables_redirect.txt

# All incoming trafic (mainly via eth2) will be redirected to 2005 (old graphite relay) 
iptables -t nat -A PREROUTING -p tcp --dport 2003 -j REDIRECT --to-port 2005
iptables -t nat -A PREROUTING -p udp --dport 2003 -j REDIRECT --to-port 2005
# Another example using ips
#iptables -t nat -A PREROUTING -i eth2 -p udp -d 10.9.2.197 --dport 2003 -j REDIRECT --to-port 2005

# loopback traffic do not go via PREROUTING chain 
iptables -t nat -A OUTPUT -o lo -p tcp --dport 2003 -j REDIRECT --to-port 2005
# just the same but using ips instead of interfaces (for udp)
iptables -t nat -A OUTPUT --src 0/0 --dst 127.0.0.1 -p udp --dport 2003 -j REDIRECT --to-port 2005

# Show it 
iptables -t nat -L -n -v