Hello All
I want to use apache-2.2.14 web server as a transparent proxy in ip layer on freebsd-7.0.
I configured it with following scenario:

Client1                                                    Apache TProxy Configured                                  web server
172.20.13.43 ---------------- [em0:172.20.13.196,   192.168.100.101:em1] --------------------192.168.100.102

My httpd.conf on Tproxy is:
....
Listen 4129
<VirtualHost 172.20.13.196:4129>
        ServerName 172.20.13.196
        ProxyRequests off
        ProxyTProxy On
        ProxyPass / http://192.168.100.102/
        ProxyPassReverse / http://192.168.100.102/
        ProxyPreserveHost On
</VirtualHost>

I used ipnat for trrafic redirection by following configuration.
/etc/ipnat.conf:
rdr em0 192.168.100.102/32 port 80 -> 172.20.13.196 port 4129 tcp

when i request http://192.168.100.102 on web client1, i recieve following error on web browser:

Service Temporarily Unavailable

The server is temporarily unable to service your request due to maintenance downtime or capacity problems. Please try again later.

My apache error log is:
[Sat Oct 15 11:59:45 2011] [debug] mod_proxy_http.c(56): proxy: HTTP: canonicalising URL //192.168.100.102/
[Sat Oct 15 11:59:45 2011] [debug] proxy_util.c(1494): [client 172.20.13.43] proxy: http: found worker http://192.168.100.102/ for http://192.168.100.102/
[Sat Oct 15 11:59:45 2011] [debug] mod_proxy.c(993): Running scheme http handler (attempt 0)
[Sat Oct 15 11:59:45 2011] [debug] mod_proxy_http.c(1940): proxy: HTTP: serving URL http://192.168.100.102/
[Sat Oct 15 11:59:45 2011] [debug] proxy_util.c(1999): proxy: HTTP: has acquired connection for (192.168.100.102)
[Sat Oct 15 11:59:45 2011] [debug] proxy_util.c(2055): proxy: connecting http://192.168.100.102/ to 192.168.100.102:80
[Sat Oct 15 11:59:45 2011] [debug] proxy_util.c(2153): proxy: connected / to 192.168.100.102:80
[Sat Oct 15 11:59:45 2011] [error] (22)Invalid argument: proxy: error binding to socket 172.20.13.43:4536
[Sat Oct 15 11:59:45 2011] [debug] proxy_util.c(2017): proxy: HTTP: has released connection for (192.168.100.102)

How i can fix it?
Any help would be great.

--

Best regards
Dariush Zahedmanesh