I'm using NAT mode for guest networking. I need my machines to be accessible from outside the guest. I've set up iptables to port forward a specific port on host to port 22 on guest, but this does not seem to work.
I added this rules:
# Port Forwardings
-A PREROUTING -i eth0 -p tcp --dport 9867 -j DNAT --to-destination 192.168.122.136:22
# Forward traffic through eth0 - Change to match you out-interface
-A POSTROUTING -s 192.168.1.0/24 -o eth0 -j MASQUERADE
When I ssh 192.168.122.136 from host it works perfectly, however when I try ssh 192.168.122.136 -p 9867 it shows ssh: connect to host 192.168.122.1 port 9867: Connection refused
I've enabled port forwarding on /etc/ufw/sysctl.conf
using iptables -t nat -L shows that the rule is set up on iptable
DNAT tcp -- anywhere anywhere tcp dpt:9867 to:192.168.122.136:22
Found my answer here. basicly I changed the above to
# connections from outside
iptables -t nat -A PREROUTING -p tcp --dport 9867 -j DNAT --to 192.168.122.136:22
# for local connection
iptables -t nat -A OUTPUT -p tcp --dport 9867 -j DNAT --to 192.168.122.136:22
# Masquerade local subnet
iptables -t nat -A POSTROUTING -s 192.168.122.0/24 -j MASQUERADE
iptables -A FORWARD -o virbr0 -m state --state RELATED,ESTABLISHED -j ACCEPT
iptables -A FORWARD -i virbr0 -o eth0 -j ACCEPT
iptables -A FORWARD -i virbr0 -o lo -j ACCEPT
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I have this bash script configuring iptables with rules allowing input and output on port 22 and i cant connect on ssh (ssh is configured on port 22 on the server).
I first flush rules, then set default policy to drop, then drop icmp request, then drop xmas and null scan, drop broadcast, allow open connection to receive packets, accept local loop, accept incoming traffic on specified ports, then allow outgoing traffic with specified rules...
#/bin/bash
set -ex
# Flush all existing rules, chains, and tables
iptables -F
iptables -X
iptables -t nat -F
iptables -t nat -X
iptables -t mangle -F
iptables -t mangle -X
# create table
# Not necessary in iptables
# set default policy to drop
iptables -P INPUT DROP
iptables -P OUTPUT DROP
iptables -P FORWARD ACCEPT
# Drop all incoming ipv6 traffic
#iptables -A INPUT -p ipv6 -j DROP
# Drop all outgoing ipv6 traffic
#iptables -A OUTPUT -p ipv6 -j DROP
# Drop all forwarded ipv6 traffic
#iptables -A FORWARD -p ipv6 -j DROP
############### INPUT chain
## On drop les requêtes ICMP (votre machine ne répondra plus aux requêtes ping sur votre réseau local).
iptables -A INPUT -p icmp --icmp-type echo-request -j DROP
## On accepte le Multicast.
#iptables -A INPUT -m pkttype --pkt-type multicast -j ACCEPT
## On drop les scans XMAS et NULL.
iptables -A INPUT -m conntrack --ctstate INVALID -p tcp --tcp-flags FIN,URG,PSH FIN,URG,PSH -j DROP
iptables -A INPUT -m conntrack --ctstate INVALID -p tcp --tcp-flags ALL ALL -j DROP
iptables -A INPUT -m conntrack --ctstate INVALID -p tcp --tcp-flags ALL NONE -j DROP
iptables -A INPUT -m conntrack --ctstate INVALID -p tcp --tcp-flags SYN,RST SYN,RST -j DROP
## Dropper silencieusement tous les paquets broadcastés.
iptables -A INPUT -m pkttype --pkt-type broadcast -j DROP
## Permettre à une connexion ouverte de recevoir du trafic en entrée.
iptables -A INPUT -m conntrack --ctstate ESTABLISHED -j ACCEPT
## On accepte la boucle locale en entrée.
iptables -I INPUT -i lo -j ACCEPT
#Server rules
iptables -A INPUT -p tcp -m tcp --sport 22 -i enp53s0 -j ACCEPT
iptables -A INPUT -p tcp -m tcp --sport 80 -i enp53s0 -j ACCEPT
iptables -A INPUT -p tcp -m tcp --sport 8080 -i enp53s0 -j ACCEPT
iptables -A INPUT -p tcp -m tcp --sport 443 -i enp53s0 -j ACCEPT
# Drop invalid packets
iptables -A INPUT -m state --state INVALID -i enp53s0 -j DROP
## On log les paquets en entrée.
iptables -A INPUT -j LOG
############### OUTPUT chain
# Allow outgoing traffic on the loopback interface
iptables -A OUTPUT -o lo -j ACCEPT
## Permettre à une connexion ouverte de recevoir du trafic en sortie.
iptables -A OUTPUT -m conntrack ! --ctstate INVALID -j ACCEPT
# allow outgoing connection for dns requests, time synchro on enp53s0 interface
iptables -A OUTPUT -p udp -m udp --dport 53 -o enp53s0 -j ACCEPT
iptables -A OUTPUT -p udp -m udp --dport 123 -o enp53s0 -j ACCEPT
# allow connections on source and destination specific ports on enp53s0 interface
iptables -A OUTPUT -p tcp -m tcp --dport 53 -o enp53s0 -j ACCEPT
iptables -A OUTPUT -p tcp -m tcp --dport 22 -o enp53s0 -j ACCEPT
iptables -A OUTPUT -p tcp -m tcp --dport 80 -o enp53s0 -j ACCEPT
iptables -A OUTPUT -p tcp -m tcp --dport 8080 -o enp53s0 -j ACCEPT
iptables -A OUTPUT -p tcp -m tcp --dport 443 -o enp53s0 -j ACCEPT
# allow ping in output chain
iptables -A OUTPUT -p icmp --icmp-type echo-request -o enp53s0 -j ACCEPT
What am i missing?
Thank you
In the input chain, under #Server rules, you probably need to change --sport 22 to --dport 22. Similarly for the others.
I have one interface which visible to my network, and a loopback (127.0.0.1),
ens192 -> 192.168.22.100
lo -> 127.0.0.1
I have a service running on lo interface on port 3333, and I want to reach that port via ens192 via port 4444
192.168.22.100:4444 -> 127.0.0.1:3333
I have tried all available solutions on StackOverflow it doesn't work.
sysctl -w net.ipv4.conf.[IFNAME].route_localnet=1
iptables -t nat -A PREROUTING -p tcp -d 192.168.22.100 --dport 4444 -j DNAT --to 127.0.0.1:3333
iptables -A INPUT -i ens192 -p tcp --dport 4444 -m state --state NEW,ESTABLISHED -j ACCEPT
iptables -A OUTPUT -o ens192 -p tcp --sport 4444 -m state --state ESTABLISHED -j ACCEPT
I have a server on cloud with following iptables.
iptables -A INPUT -i lo -j ACCEPT
iptables -A INPUT -p tcp --dport 80 -j ACCEPT
iptables -A INPUT -p tcp --dport 443 -j ACCEPT
iptables -A INPUT -j DROP
iptables -A OUTPUT -o lo -j ACCEPT
iptables -A OUTPUT -p tcp --sport 80 -m state --state RELATED,ESTABLISHED -j ACCEPT
iptables -A OUTPUT -p tcp --sport 443 -m state --state RELATED,ESTABLISHED -j ACCEPT
iptables -A OUTPUT -p tcp --sport 9200 -m state --state New,RELATED,ESTABLISHED -j ACCEPT
iptables -A OUTPUT -j DROP
iptables -t nat -A PREROUTING -i eth0 -p tcp --dport 2900 -j DNAT --to-destination 127.0.0.1:9200
What I have to add in other chains so that i can access my service on 2900 port.
Rules apply from the top down.
6.2 Destination NAT
This is done in the PREROUTING chain, just as the packet comes in; this means that anything else on the Linux box itself (routing, packet filtering) will see the packet going to its `real' destination
https://www.netfilter.org/documentation/HOWTO/NAT-HOWTO-6.html#ss6.2
So you want the PREROUTING line at the top, so the NAT happens first.
Then an INPUT entry allowing incoming connections on your destination port, after NAT.
Except, what's up with your INPUT rules not accepting RELATED and ESTABLISHED and your output rules setting specific source ports? Outbound traffic usually comes from random high ports.
From https://serverfault.com/a/578781/57144 and https://serverfault.com/a/578787/57144 you want to explicitly say NEW connections for incoming ports, and should prefer fewer rules for performance (if applicable).
iptables -t nat -A PREROUTING -i eth0 -p tcp --dport 2900 -j DNAT --to-destination 127.0.0.1:9200
iptables -A INPUT -m state --state RELATED,ESTABLISHED -j ACCEPT
iptables -A INPUT -i lo -j ACCEPT
iptables -A INPUT -p tcp -m state --state NEW -m tcp --dport 80 -j ACCEPT
iptables -A INPUT -p tcp -m state --state NEW -m tcp --dport 443 -j ACCEPT
iptables -A INPUT -p tcp -m state --state NEW -m tcp --dport 9200 -j ACCEPT
# or
# iptables -A INPUT -p tcp -m state --state NEW -m tcp -m multiport --dports 80,443,9200 -j ACCEPT
iptables -A INPUT -j DROP
When I clear IPtables and then add the following rules, incoming connections can connect to my KVM VM on port 1234 without any problems.
-A PREROUTING -i br0 -p tcp -m tcp --dport 1234 -j DNAT --to-destination 192.168.122.194:1234
-A FORWARD -d 192.168.122.194/32 -p tcp -m state --state NEW,RELATED,ESTABLISHED -m tcp --dport 1234 -j ACCEPT
-A FORWARD -s 192.168.122.194/32 -p tcp -m tcp --sport 1234 -j ACCEPT
-A FORWARD -d 192.168.122.194/32 -p tcp -m tcp --dport 1234 -j ACCEPT
But I also want NAT to work inside my KVM VM's. By default libvirt sets up some rules that provide my VM's with NAT. However when I try sending SIGHUP to libvirt (that's how you ask it to add it's rules to iptables), it adds the following rules to iptables that breaks my port forwarding that I have specified above.
-A FORWARD -d 192.168.122.0/24 -o virbr0 -m conntrack --ctstate RELATED,ESTABLISHED -j ACCEPT
-A FORWARD -s 192.168.122.0/24 -i virbr0 -j ACCEPT
-A FORWARD -i virbr0 -o virbr0 -j ACCEPT
-A FORWARD -o virbr0 -j REJECT --reject-with icmp-port-unreachable
-A FORWARD -i virbr0 -j REJECT --reject-with icmp-port-unreachable
-A OUTPUT -o virbr0 -p udp -m udp --dport 68 -j ACCEPT
-A POSTROUTING -s 192.168.122.0/24 -d 224.0.0.0/24 -j RETURN
-A POSTROUTING -s 192.168.122.0/24 -d 255.255.255.255/32 -j RETURN
-A POSTROUTING -s 192.168.122.0/24 ! -d 192.168.122.0/24 -p tcp -j MASQUERADE --to-ports 1024-65535
-A POSTROUTING -s 192.168.122.0/24 ! -d 192.168.122.0/24 -p udp -j MASQUERADE --to-ports 1024-65535
-A POSTROUTING -s 192.168.122.0/24 ! -d 192.168.122.0/24 -j MASQUERADE
I've tried running these commands manually. I can run all of the FORWARD and OUTPUT commands and they do not break my port forwarding. However I can't run any of the POSTROUTING commands manually. I get an error saying: "No chain/target/match by that name."
*These libvirt iptables rules in the last grey section above were obtained by running iptables-save and confirming port forwarding was working, then sending SIGHUP to libvirt, confirming port forwarding was broken, then running iptables-save again and running a diff on the two outputs to find which new iptables rules were added by libvirt.
I just enabled NAT with my own rules. I didn't bother with any of the default libvirt rules.
Adding NAT is as simple as 3 iptables commands.
(where br0 is your internet facing adapter (it could be ppp0 or whatever))
iptables -t nat -A POSTROUTING -o br0 -j MASQUERADE
iptables -A FORWARD -i br0 -o virbr0 -m state --state RELATED,ESTABLISHED -j ACCEPT
iptables -A FORWARD -i virbr0 -o br0 -j ACCEPT
I have a machine with 2 interfaces:
eth0 inet addr:1.1.1.1
eth1 inet addr:2.2.2.2
eth0 is a server, eth1 is the network on virtual machine.
I have ssh on server, so 1.1.1.1:22 is busy.
I need a rule for redirecting incoming connections on eth0 port 6000 to eth1, ip 2.2.2.100 on port 22 (virtual machine ip).
In this mode if I did, on an external machine,
ssh -p 6000 root#1.1.1.1
I would login on the virtual machine.
I tried this rule but it didn't work:
sudo iptables -P FORWARD ACCEPT
sudo iptables -t nat -A PREROUTING -p tcp -i eth0 --dport 6000 -j DNAT --to 2.2.2.100:22
Well there are like 1 million scripts/tutorials/things for this case, but if someone lands from google to here is something like this:
iptables -I FORWARD -d 2.2.2.2 -m comment --comment "Accept to forward ssh traffic" -m tcp -p tcp --dport 22 -j ACCEPT
iptables -I FORWARD -m comment --comment "Accept to forward ssh return traffic" -s 2.2.2.2 -m tcp -p tcp --sport 22 -j ACCEPT
iptables -t nat -I PREROUTING -m tcp -p tcp --dport 60000 -m comment --comment "redirect pkts to virtual machine" -j DNAT --to-destination 2.2.2.2:22
iptables -t nat -I POSTROUTING -m comment --comment "NAT the src ip" -d 2.2.2.2 -o eth1 -j MASQUERADE