Both firewalld and iptables ultimately manipulate netfilter rules in the Linux kernel, but their management approaches differ significantly:

# Traditional iptables rule example
iptables -A INPUT -p tcp --dport 22 -j ACCEPT
iptables -A INPUT -j DROP

# Equivalent firewalld command
firewall-cmd --permanent --add-service=ssh
firewall-cmd --reload

Firewalld introduces dynamic management concepts missing in raw iptables:

• Zones (public, work, home, etc.) with separate rule sets
• Runtime vs permanent configurations
• Service definitions with pre-configured ports
• D-Bus interface for programmatic control

Consider traditional iptables when:

# Complex custom chains example
iptables -N CUSTOM_CHAIN
iptables -A CUSTOM_CHAIN -s 192.168.1.0/24 -j RETURN
iptables -A INPUT -j CUSTOM_CHAIN

• You need granular control over chains and tables
• Legacy systems requiring direct rule manipulation
• Custom routing/NAT configurations beyond firewalld's capabilities
• Scripts already exist using iptables-save/restore format

Firewalld excels in these scenarios:

# Managing rich rules in firewalld
firewall-cmd --permanent --zone=public \
    --add-rich-rule='rule family="ipv4" source address="192.168.1.100" port port="8080" protocol="tcp" accept'

• Dynamic environments requiring frequent rule changes
• Multi-zone configurations (e.g., laptops moving between networks)
• Systemd-integrated service management
• Enterprise environments needing D-Bus API integration

Converting an iptables rule to firewalld:

# Original iptables rule
iptables -A INPUT -p tcp --dport 3306 -s 10.0.0.0/24 -j ACCEPT

# Firewalld equivalent
firewall-cmd --permanent --zone=trusted \
    --add-rich-rule='rule family="ipv4" source address="10.0.0.0/24" port port="3306" protocol="tcp" accept'

Contrary to common misconceptions:

• Firewalld doesn't add significant overhead (still uses iptables/nftables)
• Rule processing speed is nearly identical for equivalent rulesets
• Firewalld's dynamic updates actually reduce service interruption

For most modern server deployments:

1. Start with firewalld as the default (already configured in RHEL/CentOS 7+)
2. Only disable it if you encounter specific limitations
3. For complex environments, consider combining both (manage base rules via firewalld, custom chains via direct iptables)

# Checking current firewall backend
firewall-cmd --get-backend

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While both firewalld and iptables handle packet filtering, their architectures differ significantly. Firewalld operates as a dynamic firewall manager with D-Bus interface, while iptables provides direct rule management through kernel netfilter hooks.

# iptables direct rule example
iptables -A INPUT -p tcp --dport 22 -j ACCEPT

# Equivalent firewalld command
firewall-cmd --permanent --add-service=ssh

Firewalld excels in environments requiring:

• Runtime configuration changes without service restarts
• Zone-based network segmentation (public, dmz, work, home)
• Integration with NetworkManager for mobile workstations
• XML-based configuration management with atomic updates

Consider traditional iptables when:

# Complex rule chains example
iptables -N CUSTOM_CHAIN
iptables -A CUSTOM_CHAIN -p tcp --dport 8080 -j LOG --log-prefix "WebAccess: "
iptables -A INPUT -j CUSTOM_CHAIN

• You need direct control over rule chains
• Legacy script compatibility is required
• Working with specialized network configurations (bridges, custom routing)
• Preferring direct /etc/sysconfig/iptables editing

Benchmark tests show negligible difference in packet filtering speed, as both ultimately use netfilter hooks. The real difference comes in management overhead:

Operation	Firewalld	iptables
Rule addition	~50ms	~5ms
Full ruleset reload	Atomic	Flush+reload
100 rule management	~1s	~2s

Converting iptables rules to firewalld:

# Original iptables
iptables -A INPUT -p tcp --dport 80 -j ACCEPT

# Firewalld equivalent
firewall-cmd --permanent --add-port=80/tcp
firewall-cmd --reload

For CentOS/RHEL servers:

• Use firewalld for most server deployments (default since RHEL7)
• Consider iptables for legacy applications or complex networking
• For containerized environments, firewalld's rich rules integrate better

# Docker + firewalld integration example
firewall-cmd --permanent --zone=trusted --add-interface=docker0
firewall-cmd --permanent --zone=public --add-masquerade

Firewalld offers capabilities beyond basic iptables:

# Time-based rules
firewall-cmd --add-rich-rule='rule family="ipv4" source address="192.168.1.0/24" port port="22" protocol="tcp" accept' --timeout=300

# Direct passthrough for complex rules
firewall-cmd --direct --add-rule ipv4 filter INPUT 0 -p tcp --dport 3306 -s 10.0.0.0/24 -j ACCEPT