In this guide from PerLod Hosting, you will learn the differences between iptables vs nftables for high-traffic Linux servers, which focuses on performance and long-term maintainability. You can discover how each firewall framework evaluates packets, how rule structure and rule count can impact throughput and latency, and why rule management becomes a bottleneck on high-traffic systems.

Also, you will learn how rules are written in each system, including common patterns like allowing services, dropping unwanted traffic, and using sets for large allow and deny lists, and then you will learn a safe migration path from iptables to nftables.

The goal is to help choose the right firewall option between iptables vs nftables for production environments. For dedicated servers handling high-traffic workloads, choosing the right firewall framework directly impacts performance and stability.

iptables vs nftables Performance

At this point, you can discover how fast iptables vs nftables can handle network traffic on high-traffic servers. When traffic is high, the firewall should filter packets with the least possible CPU load and the smallest delay.

Core Performance Architecture Differences in iptables vs nftables:

• iptables checks rules one by one in order, so when you have lots of rules, it can get slower because each packet may need to be compared against many rules.
• nftables can use faster lookup methods like sets, so matching can stay quick even when the list of addresses or ports becomes very large.

Key Performance Metrics from Benchmark Studies:

One academic study tested both firewalls with different packet sizes and different numbers of rules, then measured throughput and latency using iPerf3 and ICMP ping-style checks.

It found that when rules are checked in a simple one-by-one way, nftables could be slower than iptables for very small packets, including 64 to 256 bytes, when the ruleset is very large, including 1000 and higher rules. But when nftables uses faster indexed lookups like set-based matching, the performance was almost the same as iptables, and nftables was sometimes a bit faster with bigger packets and medium-sized rule sets.

Real-World High-Traffic Benchmarks in iptables vs nftables:

The SKUDONET benchmarks showed that nftables handled a lot more load‑balancing traffic per CPU core than iptables.

• DNAT (destination NAT): iptables around 256k requests/sec per core, nftables around 561k requests/sec per core (about +118%).
• SNAT (source NAT): iptables around 262k requests/sec per core, nftables around 609k requests/sec per core (about +132%).

They also found that when you add more backend servers, iptables performance drops faster because it has to check more rules one by one, while nftables scales better because it can match using more efficient structures.

CPU and Memory Efficiency in iptables vs nftables:

Red Hat’s tests showed that iptables usually gets slower as you add more rules, because it has to check more items for each packet. The nftables can scale better, because it can organize rules using things like sets instead of long one-by-one lists.

In one test, 100,000 packets per second with a blacklist check, iptables needed a bigger CPU hit than nftables:

• iptables: about 40.77% extra CPU cost
• nftables: about 17.27% extra CPU cost

Memory can also be very different. With iptables, large IP lists often mean lots of separate entries, so memory usage can grow fast. nftables can store large lists more efficiently using sets, so it typically uses less memory for big allow and deny lists.

Latency and Throughput Characteristics:

On high-traffic servers, it’s not just the average speed that matters; it’s how stable the latency stays when the system is under heavy load.

In Kubernetes tests from 2025, when the setup had 30,000 services, nftables stayed more consistent. Its slowest normal latency (p99) was about as good as iptables’ latency (p01). That suggests nftables can deliver more predictable latency when things get extremely large and busy.

Performance Recommendation Between iptables vs nftables: For servers handling over 10,000 concurrent connections or 1 Gbps sustained traffic, nftables provides better performance through:

• Hash-based set matching for IP and port blacklists.
• Atomic rule updates, which prevent little configuration states.
• Early ingress hooks process packets before conntrack overhead.

iptables vs nftables Rules

In this step, you can learn how iptables vs nftables rules are structured. The goal is to make the syntax differences clear and show why nftables often stay cleaner when rule sets grow.

1. Syntax and Command Structure Comparison:

iptables Commands Example:

iptables -t filter -A INPUT -p tcp --dport 22 -j ACCEPT
iptables -t filter -A INPUT -p tcp --dport 80 -j ACCEPT
iptables -t filter -A INPUT -p tcp --dport 443 -j ACCEPT

nftables Commands Example:

nft add rule ip filter input tcp dport 22 accept
nft add rule ip filter input tcp dport {80, 443} accept

nftables can put multiple ports into one rule by using a set, so you end up with about 66% fewer rules in this example.

2. Set and Map Implementations:

iptables IP Set Configuration:

# Requires separate ipset utility
ipset create blacklist hash:ip hashsize 65536 maxelem 1000000
iptables -A INPUT -m set --match-set blacklist src -j DROP

nftables Native Set Implementation:

nft add set ip filter blacklist { type ipv4_addr\; flags interval\; }
nft add element ip filter blacklist { 192.168.1.0/24, 10.0.0.0/8 }
nft add rule ip filter input ip saddr @blacklist drop

nftables has built-in sets that can handle IP ranges, and you manage them directly in nftables rules without needing extra tools. This makes updates safer because changes apply all at once, and it usually uses less memory when you have very large blacklists.

3. Multi-Action Rules and Logging:

iptables requires separate rules for logging and dropping:

iptables -A FORWARD -p tcp --dport 22 -j LOG --log-prefix "SSH: "
iptables -A FORWARD -p tcp --dport 22 -j DROP

nftables combines actions in a single rule:

nft add rule ip filter forward tcp dport 22 log prefix "SSH: " drop

It means the firewall has fewer steps to check for each matching connection, because logging and dropping happen in one rule instead of two, so the rule processing task can be cut roughly in half in that case.

4. IPv4 and IPv6 Unified Configuration:

iptables requires duplicate rules:

iptables -A INPUT -p tcp --dport 80 -j ACCEPT
ip6tables -A INPUT -p tcp --dport 80 -j ACCEPT

nftables inet family handles both protocols:

nft add rule inet filter input tcp dport 80 accept

Using the inet family lets you write one rule that works for both IPv4 and IPv6, instead of writing the same rule twice. This makes the firewall config easier to manage and lowers the chance of mistakes like updating IPv4 rules but forgetting IPv6.

5. Connection Tracking Optimization:

iptables conntrack interaction:

iptables -A INPUT -m conntrack --ctstate ESTABLISHED,RELATED -j ACCEPT

nftables native state tracking:

nft add rule ip filter input ct state established,related accept

nftables can check connection states directly inside the rule itself, instead of relying on extra matching layers. This can reduce extra processing tasks and help the system run a bit more efficiently, especially on high-traffic servers.

How to Migrate from iptables to nftables?

At this point, you learn how to migrate from iptables to nftables in a safe and low-risk way, especially on production servers where a mistake can cause downtime or lock you out.

First, you must check the current backend implementation with the command below:

sudo update-alternatives --display iptables

In the output, you must see iptables-legacy or iptables-nft backend.

You must back up the existing rulesets by using the following commands:

sudo iptables-save > /root/iptables-backup-$(date +%Y%m%d).rules
sudo ip6tables-save > /root/ip6tables-backup-$(date +%Y%m%d).rules

Remember to store the backups in version control or a secure location.

Now you can convert rules with iptables-restore-translate:

# On RHEL 8+ or Ubuntu 20.04+
sudo iptables-restore-translate -f /root/iptables-backup.rules > /etc/nftables.conf

This converts your iptables rules into nftables rules automatically, while keeping the same rule order and behavior.

Once you are done, validate converted rules with the command below:

sudo nft -c -f /etc/nftables.conf

The -c flag checks syntax without applying rules. No output means successful validation.

Here is an example of how one common iptables NAT rule translates into nftables:

iptables -t nat -A POSTROUTING -s 10.0.0.0/8 -o eth0 -j SNAT --to-source 203.0.113.5

Equivalent nftables configuration:

nft add table ip nat
nft add chain ip nat postrouting { type nat hook postrouting priority 100\; }
nft add rule ip nat postrouting ip saddr 10.0.0.0/8 oif eth0 snat to 203.0.113.5

At this point, you must flush legacy rules and activate nftables with the commands below:

sudo iptables -F
sudo iptables -X
sudo nft flush ruleset
sudo systemctl enable --now nftables

Verify active configuration with the command below:

sudo nft list ruleset

Check that the new rules do the same thing as your old iptables rules.

Note: If connectivity issues happen, you can restore iptables rules immediately with the commands below:

sudo systemctl stop nftables
sudo iptables-restore < /root/iptables-backup-$(date +%Y%m%d).rules
sudo systemctl disable nftables

Keep a direct console session open while migrating, so if the firewall rules cut off SSH, you can still log in and fix or roll back the change.

Best Practices for iptables to nftables Migration

Here are the best practices you can consider for iptables to nftables migration:

1. Staging Environment Testing: Validate converted rules on non-production systems, matching production hardware and traffic patterns.
2. Incremental Migration: Migrate one server role at a time to isolate issues.
3. ​Monitoring: Implement metrics collection for packet processing latency before and after migration using perf or bpftrace.
4. Documentation: Maintain version-controlled nftables.conf files with change history and rollback tags.

After successful migration, you can optimize for nftables-specific features:

Implement performance-focused sets:

# Create optimized blacklist set
nft add set inet filter blacklist { type ipv4_addr\; flags timeout,interval\; }
nft add element inet filter blacklist { 192.0.2.0/24 timeout 1d }

Use early ingress hooks for DDoS mitigation:

nft add table netdev filter
nft add chain netdev filter ingress { type filter hook ingress device eth0 priority -500\; }
nft add rule netdev filter ingress ip saddr @blackdrop drop

Early ingress hooks process packets before conntrack, which reduces CPU usage by 15 to 20% during attacks.

Distribution-Specific Migration Notes:

• RHEL and CentOS 8+: Uses nftables by default. Run iptables-nft for the compatibility layer.
• Ubuntu 20.04+: Supports direct nftables usage. Install the nftables package and disable ufw if present.
• Debian 10+: Migrate using iptables-restore-translate then switch default backend:

sudo update-alternatives --set iptables /usr/sbin/iptables-nft

This ensures legacy scripts continue functioning while using the nftables kernel backend.

Best Recommendation: For high-traffic servers like 1 Gbps or 10,000+ active connections, nftables is often the better choice because it can handle large rule sets more efficiently and is easier to manage as things grow.

Moving from iptables to nftables takes some planning, but it usually pays off long-term because updates apply all at once, one ruleset can cover both IPv4 and IPv6, and large allow and deny lists can be handled efficiently with sets.

FAQs

Conclusion

iptables is old and reliable, but it can get slow on high-traffic servers because it checks rules one by one. nftables is newer, easier to manage, and can be faster because it handles large rule sets more efficiently. On high-traffic systems like 1 Gbps+ traffic or thousands of connections, nftables can scale better and reduce CPU load, especially when using sets for big allow and deny lists.

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