LinuxA & LinuxB
linuxA:eth0(10.1.1.1) connected linuxB:eth0 (10.1.1.2)
linuxA:eth1(202.1.20.45) connected internet
linuxB:eth1(202.1.20.46) connected internet
LinuxA & LinuxB gw 202.1.20.33
user via internet access LinuxA tcp port 1935 , LinuxA trans this port to LinxB port 1935,

On LinuxA ,setting:
Iptables –t nat –A PREROUTING –d 202.1.20.45
–p tcp –dort 1935 -j DNAT –to 10.1.1.2:1935
iptables -t nat -A POSTROUTING -s 10.1.1.2
--sport 1935 -j**SNAT --to 202.1.20.45
but failed , because gateway ? any other ways ?

Attached Thumbnails

 

Iptables –t nat –A PREROUTING –d 202.1.20.45
Does this statement is valid on LinuxA , which data is going on destionation 202.1.20.45 from linuxA ? I mean 202.1.20.45 is source ip not destination for originating data.

Thanks

tcpdump on LnuxA:

[root@hz2 ~]# tcpdump port 1935 -i eth1
tcpdump: verbose output suppressed, use -v or -vv for full protocol decode
listening on eth1, link-type EN10MB (Ethernet), capture size 96 bytes
15:52:40.765232 IP 209.158.224.171.43415 > 202.1.20.45.macromedia-fcs: S 1076020852:1076020852(0) win 65535 <mss 1460,nop,wscale 3,nop,nop,timestamp 0 0,nop,nop,sackOK>
15:52:40.771153 IP 209.158.224.171.43415 > 202.1.20.46.macromedia-fcs: S 1076020852:1076020852(0) win 65535 <mss 1460,nop,wscale 3,nop,nop,timestamp 0 0,nop,nop,sackOK>
15:52:43.726252 IP 209.158.224.171.43415 > 202.1.20.45.macromedia-fcs: S 1076020852:1076020852(0) win 65535 <mss 1460,nop,wscale 3,nop,nop,timestamp 0 0,nop,nop,sackOK>
15:52:43.726270 IP 209.158.224.171.43415 > 202.1.20.46.macromedia-fcs: S 1076020852:1076020852(0) win 65535 <mss 1460,nop,wscale 3,nop,nop,timestamp 0 0,nop,nop,sackOK>
15:52:49.660801 IP 209.158.224.171.43415 > 202.1.20.45.macromedia-fcs: S 1076020852:1076020852(0) win 65535 <mss 1460,nop,wscale 3,nop,nop,timestamp 0 0,nop,nop,sackOK>
15:52:49.660819 IP 209.158.224.171.43415 > 202.1.20.46.macromedia-fcs: S 1076020852:1076020852(0) win 65535 <mss 1460,nop,wscale 3,nop,nop,timestamp 0 0,nop,nop,sackOK>

209.158.224.171 is USER's IP