Recently we have configured Varnish on our server, it was successfully setup but we noticed that if we open any page in multiple browsers, the Varnish send request to Apache not matter page is cached or not. If we refresh twice on each browser it creates duplicate copies of the same page.

What exactly should happen:

If any page is cached by Varnish, the subsequent request should be served from Varnish itself when we are opening the same page in browser OR we are opening that page from different IP address.

Following is my default.vcl file

backend default {
    .host = "127.0.0.1";
    .port = "80";
}

sub vcl_recv {
    if( req.url ~ "^/search/.*$")
    {
    }else {
        set req.url = regsub(req.url, "\?.*", "");
}

if (req.restarts == 0) {
    if (req.http.x-forwarded-for) {
        set req.http.X-Forwarded-For = req.http.X-Forwarded-For + ", " + client.ip;
    } else {
        set req.http.X-Forwarded-For = client.ip;
    }
}

if (!req.backend.healthy) {
    unset req.http.Cookie;
}

set req.grace = 6h;

if (req.url ~ "^/status\.php$" ||
        req.url ~ "^/update\.php$" ||
        req.url ~ "^/admin$" ||
        req.url ~ "^/admin/.*$" ||
        req.url ~ "^/flag/.*$" ||
        req.url ~ "^.*/ajax/.*$" ||
        req.url ~ "^.*/ahah/.*$") {
            return (pass);
}

if (req.url ~ "(?i)\.(pdf|asc|dat|txt|doc|xls|ppt|tgz|csv|png|gif|jpeg|jpg|ico|swf|css|js)(\?.*)?$") {
    unset req.http.Cookie;
}

if (req.http.Cookie) {
    set req.http.Cookie = ";" + req.http.Cookie;
    set req.http.Cookie = regsuball(req.http.Cookie, "; +", ";");    
    set req.http.Cookie = regsuball(req.http.Cookie, ";(SESS[a-z0-9]+|SSESS[a-z0-9]+|NO_CACHE)=", "; \1=");
    set req.http.Cookie = regsuball(req.http.Cookie, ";[^ ][^;]*", "");
    set req.http.Cookie = regsuball(req.http.Cookie, "^[; ]+|[; ]+$", "");

        if (req.http.Cookie == "") {
            unset req.http.Cookie;
        }
        else {
            return (pass);
        }
}

if (req.request != "GET" && req.request != "HEAD" &&
    req.request != "PUT" && req.request != "POST" &&
    req.request != "TRACE" && req.request != "OPTIONS" &&
    req.request != "DELETE") 
    {return(pipe);}     /* Non-RFC2616 or CONNECT which is weird. */

if (req.request != "GET" && req.request != "HEAD") {
    return (pass);
}

if (req.http.Accept-Encoding) {
    if (req.url ~ "\.(jpg|png|gif|gz|tgz|bz2|tbz|mp3|ogg)$") {
        # No point in compressing these
        remove req.http.Accept-Encoding;
    } else if (req.http.Accept-Encoding ~ "gzip") {
            set req.http.Accept-Encoding = "gzip";
    } else if (req.http.Accept-Encoding ~ "deflate") {
            set req.http.Accept-Encoding = "deflate";
    } else {
        # unknown algorithm
        remove req.http.Accept-Encoding;
    }
}
    return (lookup);
}

sub vcl_deliver {
    if (obj.hits > 0) {
        set resp.http.X-Varnish-Cache = "HIT";
    }
    else {
        set resp.http.X-Varnish-Cache = "MISS";
    }
}

sub vcl_fetch {
    if (beresp.status == 404 || beresp.status == 301 || beresp.status == 500) {
        set beresp.ttl = 10m;
}
if (req.url ~ "(?i)\.(pdf|asc|dat|txt|doc|xls|ppt|tgz|csv|png|gif|jpeg|jpg|ico|swf|css|js)(\?.*)?$") {
    unset beresp.http.set-cookie;
}
    set beresp.grace = 6h;
}

sub vcl_hash {
    hash_data(req.url);
    if (req.http.host) {
        hash_data(req.http.host);
    } else {
        hash_data(server.ip);
    }
    return (hash);
}

sub vcl_pipe {
    set req.http.connection = "close";
}

sub vcl_hit {
    if (req.request == "PURGE") 
        {ban_url(req.url);
    error 200 "Purged";}

    if (!obj.ttl > 0s)
        {return(pass);}
}

sub vcl_miss {
    if (req.request == "PURGE") 
        {error 200 "Not in cache";}
}