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Guide · Call of Duty 4

Installing CoD4X for Reign of the Undead

Get Call of Duty 4 running on the CoD4X client, add the one launch option our server needs, and join the GRN zombie server. About ten minutes, most of it downloading.

About the serverLeaderboards

CoD4X is the community client and server for Call of Duty 4: Modern Warfare. Our Reign of the Undead server runs on it, so your game needs the CoD4X client too. There are two ways to get it. The CB Servers Launcher installs and updates CoD4X for you and is the easiest. The official CoD4X installer works on a Steam copy. Pick one; you do not need both. Each tool's own documentation is the authoritative reference and is linked at every step.

Option A · easiest

CB Servers Launcher

01

Download the CB Servers Launcher

  1. Get cb-launcher.exe from the CB Servers Launcher download page and run it from any folder. It is a free, open-source launcher for community Call of Duty clients, CoD4X included. Windows 10 or newer; on Linux or Steam Deck it runs through Proton (their Linux guide).
  2. If a game later complains about missing DLLs, run the redistributables script from the launcher's Support page. Their install guide covers this.
02

Set up Modern Warfare (CoD4X)

  1. Open the Library tab, pick Modern Warfare and press SETUP.
  2. Already have CoD4 on Steam or disc? Choose the existing-install option and point it at the folder that holds iw3mp.exe, usually C:\Program Files (x86)\Steam\steamapps\common\Call of Duty 4. Then press VERIFY.
  3. No copy installed? The launcher's SETUP has its own game-files option, explained in their CoD4X page. The game is also on Steam.
03

Add the GRN launch option

  1. Press the cog on the Modern Warfare page and paste this into Launch arguments. Our server raises CoD4's asset limits for the extra guns and maps, and a client without the same line crashes while joining.
+set r_xassetnum "image=4096 material=4096 xmodel=2048 xanim=4096 fx=800"
04

Play and connect

  1. Choose the CoD4X client if it asks, then press PLAY.
  2. In game, open the console with ~, paste the connect command and press Enter.
/connect 167.114.157.225:30028

Option B

Official CoD4X installer on a Steam copy

01

Install CoD4 on Steam

  1. Install Call of Duty 4: Modern Warfare from Steam. The Steam version is already on patch 1.7, which CoD4X needs. A disc copy must be patched to 1.7 first.
02

Run the official CoD4X installer

  1. Download the latest CoD4x Setup.exe (21.5 at the time of writing) from the official CoD4X release thread.
  2. Run it and point it at your Call of Duty 4 folder, the one holding iw3mp.exe. It updates itself afterwards.
  3. Antivirus sometimes flags the modified game binary. Allow it; only ever download it from cod4x.ovh.
03

Add the launch option

  1. Right-click the CoD4X multiplayer shortcut the installer made → Properties, and add the line below to the end of Target, after a space. If you launch through Steam instead, paste it into Properties → Launch Options.
+set r_xassetnum "image=4096 material=4096 xmodel=2048 xanim=4096 fx=800"
04

Start multiplayer and connect

  1. Start multiplayer from that shortcut. Under Options → Multiplayer, set Allow Downloading to Yes, or the mod cannot download.
  2. Open the console with ~, paste the connect command and press Enter.
/connect 167.114.157.225:30028

Once you're in

First join

  • Pick a class when the menu opens: Soldier, Medic, Engineer, Armored, Scout or Assassin.
  • Kill zombies to earn points, then spend them at the shop on guns, turrets and barricades.
  • Type $bank in chat to see your saved points, $deposit and $withdraw to move them between maps.
  • Every finished game shows up on the leaderboards.

When it breaks

Errors, and what they actually mean

The game closes while joining, or says Exceeded limit of … assets

The launch option is missing or mistyped. Our server raises CoD4's image, material, model, animation and effect limits, and your client needs the same numbers. Copy the line from this page exactly, including the quotes, into Launch arguments (CB launcher) or Launch Options (Steam).

It sits on the download screen for ages

The first join downloads the RotU mod, our extra guns and the map you are joining, several hundred megabytes in total. Let it finish. Later joins only fetch maps you have not played yet.

Couldn't load image … or a map crashes on load

A download was interrupted. Close the game and delete the downloaded mods\rotu-r-alpha folder, which is in your Call of Duty 4 folder or under %LOCALAPPDATA%\CallofDuty4MW. If only one map fails, delete that map's folder under usermaps instead. Then reconnect so it downloads cleanly.

Server requires downloads but you have them disabled

Options → Multiplayer → Allow Downloading → Yes, then connect again.

Key code in use

Restart Steam and the game. If you run two copies on one key, only one can be online at a time.

The server list is empty

The master list sometimes fails to load. Connect by address instead; the console command on this page does not use the list at all.

Update backend unavailable

The CoD4X updater could not reach its server. Start it again through the CB launcher or the CoD4X installer so it can update, then launch.

Still broken?

Launcher and client problems belong with the people who make them: CB Servers docs and CoD4X client support. For anything about our server, ask in Discord with your in-game name and what you have tried.

Ask in Discord