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! At 2011-06-27，"Marian Marinov" <mm at 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 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/20110627/8d0ade33/attachment-0005.html>