On Monday 27 June 2011 07:15:33 muiz wrote:
Marian, I'm very happy you're online :)I think I have try the record you mention just now. And I would like to clear what I have done (the scripts I test):/sbin/iptables -t nat -A PREROUTING -j DNAT -p tcp --dport 8080 --to a.b.c.d:8181 /sbin/iptables -t nat -A POSTROUTING -j SNAT -s 192.168.0.0/255.255.255.0 --to 192.168.1.250 echo 1 > /proc/sys/net/ipv4/ip_fowardThen it's not to work!
You have to have some other iptables rules that block the traffic since this has to work.
Marian
At 2011-06-27，"Marian Marinov" mm@yuhu.biz wrote:
On Monday 27 June 2011 06:50:27 muiz wrote:
Dear Marian and all,
It seems don't works: /sbin/iptables -t nat -A PREROUTING -j DNAT -p tcp --dport 8080 --to a.b.c.d:8181 /sbin/iptables -t nat -A POSTROUTING -j SNAT -s 192.168.0.0/255.255.255.0 --to a.b.c.d echo 1 > /proc/sys/net/ipv4/ip_foward
Yup, its normal not to work... You got the SNAT rule wrong :)
It should be to the IP of the server that is DOING the forwarding...
so
/sbin/iptables -t nat -A POSTROUTING -j SNAT -s 192.168.0.0/255.255.255.0 --to 192.168.1.250
Marian
I check the Fedora iptables setting: /etc/sysconfig/iptables files: ...
:POSTROUTING ACCEPT [0:0]
-A PREROUTING -i eth+ -p tcp --dport 8080 -j DNAT --to-destination a.b.c.d:8080 ....
:OUTPUT ACCEPT [0:0]
-A FORWARD -i eth+ -m state --state NEW -m tcp -p tcp -d a.b.c.d --dport 8080 -j ACCEPT
And more rules I add is : /sbin/iptables -t nat -A POSTROUTING -d a.b.c.d -p tcp --dport 8080 -j MASQUERADE
Then it works! But if I don't use system-config-firewall GUI tools, then how?
Thanks very much !
At 2011-06-27，"Marian Marinov" mm@yuhu.biz wrote:
On Monday 27 June 2011 00:08:08 muiz wrote:
Thanks Marian, The server only has one IP. I think I should add more iptables records, only one NAT record is not enough,isit correct? If yes , then how?
Huh, I'm sorry yes you need a second rule. So the rules are: iptables -t nat -A PREROUTING -j DNAT -p tcp --dport 8080 --to a.b.c.d:8181 iptables -t nat -A POSTROUTING -j SNAT -s local_ip/local_net --to 192.168.1.250 echo 1 > /proc/sys/net/ipv4/ip_foward
The Source NAT(SNAT) rule is needed, cause otherwise the packaets that reach a.b.c.d will be comming from the ip of the local client not 192.168.1.250 and so 192.168.1.250 will never receive the replies from a.b.c.d. Since the packets reach the client directly from a.b.c.d, the client will simply disregard them and will wait for packets comming from .1.250.
So the SNAT rule changes the SOURCE IP of the packets to 1.250 so a.b.c.d will return the answares to the right source.
Marian
2011-06-26 23:38:58，"Marian Marinov" mm@yuhu.biz wrote：
On Sunday 26 June 2011 12:53:07 muiz wrote: > Dear all, > > I would like to forward a port to an internet server, but > failed. can you > > help me? Server: eth0: 192.168.1.250, Port: 8080 TCP, CentOS 5.6 > Remote server: IP: a.b.c.d Port: 8181 > > > Forward path: client1(192.168.1.10) -> 192.168.1.250:8080 > (forward) -> a.b.c.d Port: 8181 > ----------------------------------------- In Fedora, I > successfully to config the firewall using > system-config-firewall and iptables command: 1. Run > system-config-firewall > > 1.1 open local port 8080 > 1.2 add a forward rule: local 8080 to remote a.b.c.d:8181, tcp > > 2. echo 1 > /proc/sys/net/ipv4/ip_foward > 3. add a iptables rule: /sbin/iptables -t nat -A POSTROUTING -d > a.b.c.d -p tcp --dport 8181 -j MASQUERADE That's all. > > > > > Thanks !
You have to use Destination NAT for the job:
iptables -t nat -A PREROUTING -j DNAT -p tcp --dport 8080 --to a.b.c.d:8181 echo 1 > /proc/sys/net/ipv4/ip_foward
If you have more then one IPs on the local machine its a good idea to specify the destination -d 192.168.1.250
Marian
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