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 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 at 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 at 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 >> >> _______________________________________________ >> CentOS mailing list >> CentOS at centos.org >> http://lists.centos.org/mailman/listinfo/centos > >-- >Best regards, >Marian Marinov -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.centos.org/pipermail/centos/attachments/20110627/ceee75cc/attachment-0005.html>