yeah same problem here.
i found this maybe it can help
sorry my english is not so well iam from germany.
Setting Up Redirect
To enable redirect for third party custom maps to be able to run on their server, admins needs to install the "cooked server" files in their "\KFGame\BrewedPC" directory on the dedicated server.
Now unless users already have the cooked client map files installed manually or previously downloaded in their clients cache, the server will need to be set up to redirect clients without the map to download it from a redirect server. To enable this, the admin must open the PCServer-KFEngine.ini file and add a new section near the bottom of the file. The section is called [IpDrv.HTTPDownload] and should look like this:
[IpDrv.HTTPDownload]
RedirectToURL=http://redirect.tripwireinteractive.com/kf2/
Where the RedirectToURL is a web location that is a repository of the client map files. The example above is the location of Tripwire's public redirect server which will host several near complete and complete custom maps. The client map file must be named as a .kfm file.