📚 Left 4 Dead Server Guide

Original Co-Op Zombie Survival - Comprehensive Setup

📋 Quick Info

Engine:	Source Engine
Developer:	Valve Corporation
App ID:	222840
Default Port:	27015 UDP/TCP
Max Players:	8 default (4v4 Versus), up to 32 with mods
Difficulty:	Easy, Normal, Advanced, Expert
Game Modes:	Campaign, Versus, Survival
RCON:	Supported (same port as game)
Platform:	Windows, Linux
Control:	RCON, SourceMod, Console

Overview

Left 4 Dead is Valve's original co-operative first-person shooter where four "Survivors" must fight through hordes of infected zombies to reach safety. Released in 2008, L4D pioneered the co-op zombie survival genre and established the foundation for its sequel.

The game features the innovative "AI Director" system that dynamically adjusts gameplay difficulty, pacing, and item placement based on player performance. Each campaign tells the story of four survivors fighting through five chapters (maps) to reach an evacuation point.

Key Features

Co-op Campaign: 4-player cooperative story campaigns against AI hordes
Versus Mode: 4v4 multiplayer with players controlling Special Infected
Survival Mode: Hold out against endless waves in challenge maps
5 Original Campaigns: No Mercy, Crash Course, Death Toll, Dead Air, Blood Harvest
Special Infected: Boomer, Hunter, Smoker, Tank, Witch
AI Director: Dynamic difficulty and pacing system
Four Difficulty Levels: Easy, Normal, Advanced, Expert

🔌 Ports & Firewall Configuration

Required Ports

Port	Protocol	Purpose	Required
27015	UDP TCP	Game server + RCON (dual purpose)	✓ Yes
27020	UDP	SourceTV (optional spectating)	Optional

Firewall Configuration Examples

Ubuntu/Debian (UFW)

# Allow L4D game port (UDP and TCP)
sudo ufw allow 27015
sudo ufw allow 27015/tcp

# Allow SourceTV (optional)
sudo ufw allow 27020/udp

# Enable firewall
sudo ufw enable
sudo ufw status

CentOS/RHEL (FirewallD)

# Add L4D ports
sudo firewall-cmd --permanent --add-port=27015/udp
sudo firewall-cmd --permanent --add-port=27015/tcp
sudo firewall-cmd --permanent --add-port=27020/udp
sudo firewall-cmd --reload
sudo firewall-cmd --list-ports

Windows Firewall (PowerShell)

# Game server port
New-NetFirewallRule -DisplayName "L4D Server" -Direction Inbound -LocalPort 27015 -Protocol UDP -Action Allow
New-NetFirewallRule -DisplayName "L4D Server TCP" -Direction Inbound -LocalPort 27015 -Protocol TCP -Action Allow

# SourceTV (optional)
New-NetFirewallRule -DisplayName "L4D SourceTV" -Direction Inbound -LocalPort 27020 -Protocol UDP -Action Allow

iptables (Advanced)

# Allow L4D ports
iptables -A INPUT -p udp --dport 27015 -j ACCEPT
iptables -A INPUT -p tcp --dport 27015 -j ACCEPT
iptables -A INPUT -p udp --dport 27020 -j ACCEPT

# Save rules (Ubuntu/Debian)
netfilter-persistent save

# Save rules (CentOS/RHEL)
service iptables save

Installation

Prerequisites

SteamCMD installed (Installation Guide)
Adequate disk space (~15 GB for full installation)
Open firewall ports (27015 UDP/TCP minimum)
Linux: 32-bit libraries (libstdc++6:i386, lib32gcc1)

Linux Installation

# Create server directory
mkdir -p ~/l4d_server
cd ~/l4d_server

# Install 32-bit libraries (Ubuntu/Debian)
sudo dpkg --add-architecture i386
sudo apt-get update
sudo apt-get install lib32gcc1 libstdc++6:i386

# Download server files with SteamCMD
steamcmd +force_install_dir ~/l4d_server +login anonymous +app_update 222840 validate +quit

# Note: App ID 222840 is for Left 4 Dead Dedicated Server

Windows Installation

# Download SteamCMD for Windows
# Extract to C:\steamcmd\

# Create server directory
mkdir C:\l4d_server

# Run SteamCMD
C:\steamcmd\steamcmd.exe +force_install_dir C:\l4d_server +login anonymous +app_update 222840 validate +quit

⚙️ Configuration

server.cfg

Create or edit left4dead/cfg/server.cfg:

// Server Identity
hostname "My Left 4 Dead Server"
rcon_password "your_secure_rcon_password"
sv_contact "admin@yourserver.com"
sv_region 1  // 0=US East, 1=US West, 2=South America, 3=Europe

// Basic Settings
sv_lan 0  // 0=internet server, 1=LAN only
sv_password ""  // Leave empty for public, set for private server
sv_allow_lobby_connect_only 0  // Allow direct connections

// Game Settings
z_difficulty "Normal"  // Easy, Normal, Hard, Expert
mp_gamemode "coop"  // coop, versus, survival
sv_cheats 0  // Disable cheats in production

// Player Limits
sv_maxplayers 8  // Max 8 for versus (4v4)
sv_visiblemaxplayers 8

// Voice Communication
sv_voiceenable 1
sv_alltalk 0  // 0=team only, 1=all talk

// Connection Settings
sv_minrate 20000
sv_maxrate 30000
sv_mincmdrate 30
sv_maxcmdrate 67
sv_minupdaterate 30
sv_maxupdaterate 67

// Logging
log on
sv_logecho 1
sv_logfile 1
sv_log_onefile 0
sv_logbans 1

// Director AI
director_no_death_check 0  // 0=normal spawning, 1=disable death checks
director_build_up_min_interval 20  // Minimum seconds between events

// Friendly Fire
mp_friendlyfire 0  // 0=off, 1=on (often enabled in Versus)

// Download Settings
sv_allowdownload 1
sv_allowupload 1
net_maxfilesize 64  // MB

// Performance
fps_max 300  // Server FPS cap

Game Modes & Campaigns

Game Modes

Mode	Players	Description
Campaign (Coop)	1-4	Fight through story campaigns as Survivors against AI infected
Versus	4v4	Teams alternate as Survivors and Special Infected
Survival	1-4	Hold out against endless waves in small challenge maps

Official Campaigns

All 5 original campaigns included:

Campaign	Starting Map	Maps	Setting
No Mercy	`l4d_hospital01_apartment`	5	Fairfield (hospital rooftop escape)
Crash Course	`l4d_garage01_alleys`	2	Riverside (truck depot)
Death Toll	`l4d_river01_docks`	5	Rural Pennsylvania (boathouse escape)
Dead Air	`l4d_airport01_greenhouse`	5	Metro Airport (airplane escape)
Blood Harvest	`l4d_farm01_hilltop`	5	Allegheny National Forest (farmhouse finale)

Changing Maps via RCON

# Connect with RCON
rcon_password your_password
rcon changelevel l4d_hospital01_apartment

# List all maps
rcon maps *

# Change game mode
rcon mp_gamemode versus
rcon map l4d_hospital01_apartment  // Restart map in new mode

SourceMod & Plugins

Installing SourceMod

Step 1: Install MetaMod:Source

# Download from: https://www.sourcemm.net/downloads.php?branch=stable
# Extract to left4dead/ directory

# Structure should be:
left4dead/
  addons/
    metamod/
      bin/

# Verify in server console:
meta version

Step 2: Install SourceMod

# Download from: https://www.sourcemod.net/downloads.php?branch=stable
# Extract to left4dead/ directory

# Structure should be:
left4dead/
  addons/
    sourcemod/
      plugins/
      configs/

# Add yourself as admin in:
# left4dead/addons/sourcemod/configs/admins_simple.ini
"STEAM_0:1:12345678" "99:z"

# Verify in-game:
sm version

Essential Plugins

L4DToolZ: Enable 10+ player servers (bypass 8-player limit)
AdminMenu: Full admin control panel (included with SourceMod)
Simple Chat Processor: Chat colors and formatting
Basic Votes: Kick, ban, and map voting

Popular L4D Plugins

Super Versus: 8v8 Versus mode support
Survivor Bots: Enhanced bot AI and control
Competitive Spawns: Balanced Special Infected spawning for competitive play
L4D Stats: Player statistics tracking
Infected Bots Control: Manage AI Special Infected behavior

Installing Plugins

# Place .smx files in:
left4dead/addons/sourcemod/plugins/

# Reload plugins:
rcon sm plugins reload pluginname

# List all plugins:
rcon sm plugins list

# Disable a plugin:
rcon sm plugins unload pluginname

Startup Commands

Linux

#!/bin/bash
# start_l4d.sh

cd ~/l4d_server

./srcds_run -console -game left4dead \
  +map l4d_hospital01_apartment \
  +maxplayers 8 \
  +mp_gamemode coop \
  -port 27015 \
  -ip 0.0.0.0

Windows

@echo off
REM start_l4d.bat

cd C:\l4d_server

srcds.exe -console -game left4dead ^
  +map l4d_hospital01_apartment ^
  +maxplayers 8 ^
  +mp_gamemode coop ^
  -port 27015

Startup Parameters

-console - Run with visible console
-game left4dead - Specify game directory
+map mapname - Starting map
+maxplayers 8 - Maximum players (4 for coop, 8 for versus)
+mp_gamemode mode - Game mode (coop, versus, survival)
-port 27015 - Server port
-ip 0.0.0.0 - Bind to all interfaces
+exec server.cfg - Execute config file on start

🔧 Troubleshooting

Server Not in Browser

# Check sv_lan setting
sv_lan 0  // Must be 0 for internet

# Verify connection to Steam
status  // Check "Connected to Steam servers"

# Check port availability
netstat -an | grep 27015

# Wait for master server registration (5-10 minutes)

Connection Issues

Verify firewall allows UDP 27015
Check server password (sv_password)
Ensure clients can ping server IP
Verify router port forwarding

SourceMod Not Loading

# Verify directory structure
left4dead/
  addons/
    metamod/
    sourcemod/

# Check metamod first
meta version  // Should show version number

# Then check sourcemod
sm version

# Review error logs
left4dead/addons/sourcemod/logs/errors_*.log

Performance Issues

# Check server FPS
stats  // In server console

# Optimize rates
sv_minrate 20000
sv_maxrate 30000
fps_max 300

# Reduce max players if needed
sv_maxplayers 4  // For coop

AI Director Too Hard/Easy

# Change difficulty
z_difficulty Normal  // Easy, Normal, Hard, Expert

# Adjust Special Infected spawn rates
director_build_up_min_interval 20  // Seconds between events

# Tank spawn frequency
z_tank_max_players 3000  // Distance before Tank spawns

Pro Tips

L4DToolZ Plugin: Unlock 10-32 player servers for custom game modes
Versus Balance: 4v4 is standard competitive format
Custom Campaigns: L4D has active custom campaign community
Survival Mode: Great for warming up or quick sessions
RCON Management: Use HLSW or similar tools for remote management
sv_pure 2: Enable for competitive to prevent cheats
Friendly Fire: Enable in Versus for tactical gameplay

Popular server modifications compatible with Left 4 Dead:

Metamod:Source - Foundation plugin loader required for SourceMod and other Source engine plugins