MikroTik NAT Rule Not Working – Common Reasons

🔴 Problem Description

You add a NAT rule on a MikroTik router—masquerade or port forwarding—but it simply doesn’t work.
Clients can’t access the internet, or external users can’t reach an internal server, even though the rule looks correct.

This issue is extremely common, especially when NAT rules are added without fully checking interfaces, firewall rules, or routing logic.

🔍 Common Symptoms

• Internet not working behind MikroTik

• Port forwarding not accessible from outside

• NAT rule shows zero hits

• NAT works sometimes, then stops

• Works from router but not from clients

🔍 Common Reasons Why NAT Rules Fail

1️⃣ Wrong Out-Interface or Interface List

NAT rules depend heavily on the correct interface.

Common mistake:

• Using the wrong WAN interface

• WAN interface not added to WAN interface list

Example (correct masquerade):

If the interface list is wrong → NAT will never trigger.

2️⃣ NAT Rule Order Is Incorrect

Just like firewall rules, NAT rules are processed top to bottom.

Common mistake:

• A generic rule placed above a specific rule

• Disabled rule blocking the logic

Always place:

• Specific dst-nat rules at the top

• General masquerade rules below

3️⃣ Firewall Filter Rules Are Blocking Traffic

NAT does not bypass firewall filter rules.

Even if NAT is correct:

• Traffic can still be dropped in forward chain

Check for:

• Missing accept LAN → WAN rule

• Drop rules placed too early

Firewall rules and NAT must work together.

4️⃣ Missing or Incorrect Routing

NAT alone does not fix routing issues.

Check:

• Default route exists

• Gateway is reachable

• Correct routing table is used

Without proper routing, NAT will never succeed.

5️⃣ Using Masquerade in the Wrong Scenario

Masquerade is designed for dynamic WAN IPs.

Common mistake:

• Using masquerade with static public IPs and complex setups

In advanced scenarios, src-nat with a fixed address may be required instead.

6️⃣ Port Forwarding Without Allowing Forward Chain

For dst-nat (port forwarding), firewall rules are mandatory.

You must allow forwarded traffic:

Without this rule, port forwarding will silently fail.

7️⃣ Testing from Inside the Same Network (Hairpin NAT)

Trying to access a forwarded service using the public IP from inside the LAN may fail.

This is not a NAT failure—it’s a hairpin NAT issue.

Solution options:

• Use internal IP for testing

• Configure hairpin NAT properly

• 

✅ Step-by-Step Troubleshooting Checklist

1. Check NAT rule counters (hit counts)

2. Verify WAN interface and interface lists

3. Review NAT rule order

4. Confirm firewall forward rules

5. Test routing and gateway

6. Test from external network

Each step eliminates one possible failure point.

🧠 Best Practices (From Experience)

• Always comment NAT rules

• Use interface lists instead of hard interfaces

• Log NAT rules temporarily when debugging

• Keep NAT rules minimal and clean

Simple NAT setups are easier to maintain.

⚠️ Common Mistakes

• Assuming NAT fixes firewall problems

• Forgetting forward chain rules

• Copying NAT rules from another router

• Testing port forwarding from inside LAN only

🔚 Final Thoughts

When a MikroTik NAT rule doesn’t work, the problem is rarely the NAT rule itself. In most cases, the real cause is interface mismatch, firewall filtering, rule order, or routing issues. Understanding how NAT interacts with firewall and routing makes troubleshooting much faster and more reliable.

Fix the logic—not just the rule.