James Marcinek a écrit :
Hello Everyone,
I've been running my Red Hat box as a router for my small network for
the past couple of years with no problems (if it works don't fix it). I
have another live IP address that I would like use. I would like any
traffic destined for this 'new' address to forward (DNAT) traffic to a
system in my intranet. I don't want to blindly allow all traffic, just
certain ones based off of rules. I have attempted to do this a couple of
time but without success. Below is my current topology (real IP's have
been substituted for 172.10.10.x addresses:
Internet
|
|
|
-------------------------
| 172.10.10.1 eth0 |
| |
| |
| 192.168.0.1 eth1 |
-------------------------
|
|
|
Intranet (private network)
Here's what I would like to have:
Internet
|
|
|
-------------------------
| 172.10.10.1 eth0 |
| 172.10.10.2 eth0:0 |
| |
| 192.168.0.1 eth1 |
-------------------------
|
|
|
Intranet (private network)
|
----------------------------------------->172.10.10.2 traffic to
192.168.0.2
I have bound the 2 IP addresses to the external NIC on my system (RHEL
4). I have attempted at modifying the script and have reverted to my
original to start over. Here's my current config:
# First drop everything (lets you open what you want)
iptables -P INPUT DROP
iptables -P OUTPUT DROP
iptables -P FORWARD DROP
# User-defined chain for ACCEPTed TCP packets
iptables -N okay
iptables -A okay -p TCP --syn -j ACCEPT
iptables -A okay -p TCP -m state --state ESTABLISHED,RELATED -j ACCEPT
iptables -A okay -p TCP -j DROP
# INPUT chain rules
iptables -A INPUT -p ALL -i eth1 -s 192.168.0.0/24 -j ACCEPT
iptables -A INPUT -p ALL -i lo -s 127.0.0.1 -j ACCEPT
iptables -A INPUT -p ALL -i lo -s 192.168.0.1 -j ACCEPT
iptables -A INPUT -p ALL -i lo -s 172.10.10.1 -j ACCEPT
iptables -A INPUT -p ALL -i eth1 -d 192.168.0.255 -j ACCEPT
# Rules for incoming packets from the Internet
# Packets for established connections
iptables -A INPUT -p ALL -d 172.10.10.1 -m state --state
ESTABLISHED,RELATED -j ACCEPT
# TCP rules
iptables -A INPUT -p TCP -i eth0 -s 0/0 --destination-port 21 -j okay
iptables -A INPUT -p TCP -i eth0 -s 0/0 --destination-port 22 -j okay
iptables -A INPUT -p TCP -i eth0 -s 0/0 --destination-port 25 -j okay
iptables -A INPUT -p TCP -i eth0 -s 0/0 --destination-port 80 -j okay
iptables -A INPUT -p TCP -i eth0 -s 0/0 --destination-port 443 -j okay
iptables -A INPUT -p TCP -i eth0 -s 0/0 --destination-port 953 -j okay
iptables -A INPUT -p TCP -i eth0 -s 0/0 --destination-port 993 -j okay
# UDP rules
iptables -A INPUT -p UDP -i eth0 -s 0/0 --destination-port 53 -j ACCEPT
iptables -A INPUT -p UDP -i eth0 -s 0/0 --destination-port 2074 -j ACCEPT
iptables -A INPUT -p UDP -i eth0 -s 0/0 --destination-port 4000 -j ACCEPT
iptables -A INPUT -p UDP -i eth0 -s 0/0 --destination-port 953 -j ACCEPT
# ICMP rules
# FORWARD chain rules
iptables -A FORWARD -i eth1 -j ACCEPT
iptables -A FORWARD -m state --state ESTABLISHED,RELATED -j ACCEPT
# OUTPUT chain rules
iptables -A OUTPUT -p ALL -s 127.0.0.1 -j ACCEPT
iptables -A OUTPUT -p ALL -s 192.168.0.1 -j ACCEPT
iptables -A OUTPUT -p ALL -s 172.10.10.1 -j ACCEPT
# POSTROUTING
iptables -t nat -A POSTROUTING -o eth0 -j SNAT --to-source 172.10.10.1
###################
This has been working fine for me. I've been modifying it and things
haven't been going well for me I have to say. Would I would like to do
is forward any traffic that is going to eth0:0 and send it to an
internal system. I don't want everything open on this system. This is my
latest concoction:
# First drop everything (lets you open what you want)
iptables -P INPUT DROP
iptables -P OUTPUT DROP
iptables -P FORWARD DROP
iptables -t nat -P PREROUTING DROP
iptables -t nat -P POSTROUTING DROP
# PREROUTING chain rules
# iptables -t nat -i PREROUTING 1 -d 172.10.10.2 -j LOG --loglevel debug
iptables -t nat -A PREROUTING -d 172.10.10.2 -p tcp --dport 80 -j DNAT
--to-dest 192.168.0.2
iptables -t nat -A PREROUTING -d 172.10.10.2 -p tcp --dport 443 -j DNAT
--to-dest 192.168.0.2
iptables -t nat -A PREROUTING -d 172.10.10.2 -p tcp --dport 21 -j DNAT
--to-dest 192.168.0.2
iptables -t nat -A PREROUTING -d 172.10.10.2 -p tcp --dport 22 -j DNAT
--to-dest 192.168.0.2
iptables -t nat -A PREROUTING -d 172.10.10.2 -p tcp --dport 25 -j DNAT
--to-dest 192.168.0.2
iptables -t nat -A PREROUTING -d 172.10.10.2 -p tcp --dport 953 -j DNAT
--to-dest 192.168.0.2
iptables -t nat -A PREROUTING -d 172.10.10.2 -p tcp --dport 993 -j DNAT
--to-dest 192.168.0.2
iptables -t nat -A PREROUTING -d 172.10.10.2 -p udp --dport 53 -j DNAT
--to-dest 192.168.0.2
iptables -t nat -A PREROUTING -d 172.10.10.2 -p udp --dport 53 -j DNAT
--to-dest 192.168.0.2
# User-defined chain for ACCEPTed TCP packets
iptables -N okay
iptables -A okay -p TCP --syn -j ACCEPT
iptables -A okay -p TCP -m state --state ESTABLISHED,RELATED -j ACCEPT
iptables -A okay -p TCP -j DROP
# INPUT chain rules
iptables -A INPUT -p ALL -i eth1 -s 192.168.0.0/24 -j ACCEPT
iptables -A INPUT -p ALL -i lo -s 127.0.0.1 -j ACCEPT
iptables -A INPUT -p ALL -i lo -s 192.168.0.1 -j ACCEPT
iptables -A INPUT -p ALL -i lo -s 172.10.10.1 -j ACCEPT
iptables -A INPUT -p ALL -i lo -s 172.10.10.2 -j ACCEPT
iptables -A INPUT -p ALL -i eth1 -d 192.168.0.255 -j ACCEPT
# Rules for incoming packets from the Internet
# Packets for established connections
iptables -A INPUT -p ALL -d 172.10.10.1 -m state --state
ESTABLISHED,RELATED -j ACCEPT
iptables -A INPUT -p ALL -d 172.10.10.2 -m state --state
ESTABLISHED,RELATED -j ACCEPT
# TCP rules
iptables -A INPUT -p TCP -i eth0 -s 0/0 --destination-port 21 -j okay
iptables -A INPUT -p TCP -i eth0 -s 0/0 --destination-port 22 -j okay
iptables -A INPUT -p TCP -i eth0 -s 0/0 --destination-port 25 -j okay
iptables -A INPUT -p TCP -i eth0 -s 0/0 --destination-port 80 -j okay
iptables -A INPUT -p TCP -i eth0 -s 0/0 --destination-port 443 -j okay
iptables -A INPUT -p TCP -i eth0 -s 0/0 --destination-port 953 -j okay
iptables -A INPUT -p TCP -i eth0 -s 0/0 --destination-port 993 -j okay
# UDP rules
iptables -A INPUT -p UDP -i eth0 -s 0/0 --destination-port 53 -j ACCEPT
iptables -A INPUT -p UDP -i eth0 -s 0/0 --destination-port 2074 -j ACCEPT
iptables -A INPUT -p UDP -i eth0 -s 0/0 --destination-port 4000 -j ACCEPT
iptables -A INPUT -p UDP -i eth0 -s 0/0 --destination-port 953 -j ACCEPT
# ICMP rules
# FORWARD chain rules
iptables -A FORWARD -i eth1 -j ACCEPT
iptables -A FORWARD -m state --state ESTABLISHED,RELATED -j ACCEPT
# iptables -A FORWARD -i eth0 -d 192.168.0.2 -j ACCEPT
# OUTPUT chain rules
iptables -A OUTPUT -p ALL -s 127.0.0.1 -j ACCEPT
iptables -A OUTPUT -p ALL -s 192.168.0.1 -j ACCEPT
iptables -A OUTPUT -p ALL -s 172.10.10.1 -j ACCEPT
# iptables -A OUTPUT -p ALL -s 172.10.10.2 -j ACCEPT
iptables -t nat -A OUTPUT -d 172.10.10.2 -p ALL -j DNAT --to-destination
192.168.0.2
# POSTROUTING
iptables -t nat -A POSTROUTING -s 192.168.0.2 -j SNAT --to-source
172.10.10.2
iptables -t nat -A POSTROUTING -o eth0 -j SNAT --to-source 172.10.10.1
I put all of the ports that I want allowed to go to the internal system
in the PREROUTING table. Is this the right way to do it? I would hope
that somebody can look at this and tell me what I'm doing wrong and what
I'm missing.
Thanks,
James
Hi
I think you 2 problems in your rules:
- The chains in NAT table must not be set to drop. NO filtering in nat
table.
- You forgot to add the rules to autorise traffic coming from eth0:0
to your internal host. After a DNAT rule, you need to explicitely
autorise the corresponding traffic.
Ab i think, I've don't read any rule related to that.
For example, you set this rule:
iptables -t nat -A PREROUTING -d 172.10.10.2 -p tcp --dport 80 -j DNAT
--to-dest 192.168.0.2
You must set this rule:
iptables -t filter -A FORWARD -i eth0:0 -p tcp -d 192.168.0.2 --dport 80
-j ACCEPT
And the same for all incoming traffics.
Regards
Guillaume
--
Guillaume
E-mail: silencer_<at>_free-4ever_<dot>_net
Blog: http://guillaume.free-4ever.net
----
Site: http://www.free-4ever.net
