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@xxxxxxxx> 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@xxxxxxxx> 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@xxxxxxxxxx > >> http://lists.centos.org/mailman/listinfo/centos -- Best regards, Marian Marinov
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