setup varnish to listen on different port while apache listens on port 80 - apache

Question

i have setup varnish 4 to run on port 8081 while apache is configured to run on port 80.
The problem with my setup is that when i browse my domain
http//:mydomain.com:8180/.
i get a (301) permanent redirect to http//:mydomain.com/.
Due to this redirect am unable to get the difference between calling the cached domain http//:mydomain.com:8180/ visa v the uncached domain http//:mydomain.com/.
my varnish config
DAEMON_OPTS="-a :8180\
-T localhost:6082 \
-f /etc/varnish/default.vcl \
-S /etc/varnish/secret \
-s malloc,1G"
.......
also the vcl
backend mydomain {
.host = "x.x.x.x";
.port = "80";
.connect_timeout = 60s;
.first_byte_timeout = 60s;
.between_bytes_timeout = 60s;
.max_connections = 800;
}
.......
the responce header shows that apache is the one redirecting.
HTTP/1.1 301 Moved Permanently
Date: Fri, 04 Sep 2015 11:58:04 GMT
Server: Apache
X-Powered-By: PHP/5.3.3
Expires: Thu, 19 Nov 1981 08:52:00 GMT
Pragma: no-cache
X-Pingback: http//:mydomain.com/xmlrpc.php
Location: http//:mydomain.com/
Vary: Accept-Encoding
Content-Length: 0
Content-Type: text/html; charset=UTF-8
X-Varnish: 32795
Age: 0
Via: 1.1 varnish-v4
Connection: keep-alive
my question is How do i stop the redirect?

Answer 1

fixed this by adding
set req.http.host = "http//:mydomain.com";
in vlc as shown below.
if (req.http.host ~ "mydomain.com:8180") {
set req.http.host = "mydomain.com";
set req.backend_hint = mydomain;
}
by doing this we ensure that the request host is recognized by apache hence apache will not redirect