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Fix a NAT that causes issues

We'll identify double NAT, enable UPnP or port forwarding, put a gaming console in DMZ when safe—or tell you when to call a pro.

Troubleshooting · Home maintenance
15–30 min
What you'll need
  • Access to the router admin (192.168.1.1 or 192.168.0.1)
  • The ports the app or game needs (check the app or game documentation)
  • Device IP for port forwarding or DMZ
Step 1 of 10

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Steps

Goal: Identify double NAT, enable UPnP or port forwarding, and resolve NAT-related connection issues.

  • Confirm the symptom: gaming lag, VoIP dropouts, or an app that will not accept incoming connections. If the issue is general slowness, see fix-wifi-drops-or-is-slow.
  • Good: You know the symptom. Proceed to Check for double NAT.
  • Bad: Different problem—check the right guide.

Check for double NAT

Goal: Rule out double NAT before changing port rules.

  • Log into the router at 192.168.1.1 or 192.168.0.1. Check the WAN IP in the status page.
  • If the WAN IP starts with 10.x, 172.16–31.x, or 192.168.x, you likely have double NAT—two routers in a row.
  • If double NAT: remove one router from the chain, or put the ISP modem-router in bridge mode so your router does NAT.
  • Good: WAN IP is public (single NAT). Proceed to Enable UPnP.
  • Bad: Double NAT and you cannot change the modem—call your ISP.

Enable UPnP

Goal: Let the app or game auto-open ports via UPnP.

  • In the router admin, find UPnP (Universal Plug and Play) or NAT-PMP. Enable it.
  • Retest the game or VoIP app. Many games and VoIP apps use UPnP to open ports automatically.
  • Good: Connection works. You are done.
  • Bad: Still failing. Proceed to Port forwarding.

Port forwarding

Goal: Manually open the ports the app or game needs.

  • Find the ports the app or game requires (e.g. gaming: 3074 UDP for Xbox, 27015–27030 for Steam; VoIP: 5060, 10000–20000). Check the app or game documentation.
  • Assign a static IP to the device (DHCP reservation in the router or static IP on the device).
  • In the router, add a port forwarding rule: external port, internal IP, internal port, protocol (TCP/UDP).
  • Retest.
  • Good: Connection works.
  • Bad: For a gaming console only, try DMZ as a last resort—use only for a trusted device.

When to get help

Call your ISP or a network technician if:

  • The modem is in bridge mode and you still have double NAT.
  • You cannot access the router admin.
  • You need port forwarding for business or complex setups.

Provide the router model, WAN IP, and what you have tried.

Verification

  • Gaming: NAT type shows Open or Moderate in-game.
  • VoIP: Test call completes without dropouts.
  • Remote access: App accepts incoming connections from outside the network.
  • No double NAT: Router WAN IP is a public address.

Escalation ladder

Work from the device outward. Stop when the problem is fixed.

  1. Confirm symptom Identify gaming lag, VoIP dropout, or connection failure.
  2. Double NAT Check WAN IP; remove second router or use bridge mode.
  3. UPnP Enable UPnP on the router.
  4. Port forwarding Add manual port forwarding rules for the app or game.
  5. DMZ (gaming only) Put a trusted gaming console in DMZ as last resort.
  6. Call a pro ISP or network tech if router is locked or double NAT persists.

What to capture if you need help

Before calling support or posting for help, have these ready. It speeds everything up.

  • Router model and WAN IP
  • Whether double NAT is present
  • Ports the app or game needs
  • Steps already tried

Is gaming lagging, VoIP dropping, or an app failing to connect from outside?

NAT issues often affect gaming, VoIP, and remote access. Confirm the symptom before changing router settings.

Check whether the issue is gaming lag, VoIP dropouts, or an app that will not accept incoming connections. Good: you know the symptom. Bad: general "internet slow"—see fix-wifi-drops-or-is-slow.

Yes No

You can change your answer later.

Does the router WAN IP start with 10.x, 172.16–31.x, or 192.168.x?

A private WAN IP usually means double NAT—another router behind the modem.

Log into the router at 192.168.1.1 or 192.168.0.1. Check the WAN IP in status. Private (10.x, 172.16–31.x, 192.168.x): double NAT—remove one router or put the second in bridge mode. Public IP: single NAT—proceed to UPnP.

Yes (double NAT) No (single NAT)

You can change your answer later.

Remove second router or enable bridge mode

Remove one router from the chain, or put the ISP modem-router in bridge mode so your router does NAT. Retest. If double NAT is fixed, the WAN IP on your router should be public.

Done

Is UPnP enabled on the router?

UPnP lets games and VoIP apps auto-open ports. Many routers have it off by default.

In the router admin, find UPnP or NAT-PMP. Enable it. Retest the game or VoIP app. Good: connection works. Bad: still failing—add manual port forwarding.

Yes No

You can change your answer later.

Enable UPnP and retest

Enable UPnP in the router. Retest. If it works, you are done. If not, add manual port forwarding for the ports the app or game needs.

Done

Does the game or app work after UPnP?

Retest. If gaming, check NAT type (Open/Moderate/Strict). If VoIP, make a test call. Good: works. Bad: add port forwarding or DMZ for gaming console.

Yes No

You can change your answer later.

Add port forwarding or DMZ (gaming console)

Assign a static IP first, then add rules or DMZ.

Add port forwarding rules for the app or game ports. For a gaming console only, DMZ can work as last resort—use only for a trusted device. Assign a static IP to the device first. Retest.

Yes No

You can change your answer later.

Issue resolved

NAT is no longer blocking. The game or app should connect.

Done

Issue may not be NAT-related

If the symptom is not gaming lag, VoIP dropouts, or incoming connection failure, see fix-wifi-drops-or-is-slow or search for your specific symptom.

Done

Call a pro

If you cannot fix double NAT or access the router, contact your ISP or a network technician. Provide the router model and what you have tried.

Done

Reviewed by Blackbox Atlas

Frequently asked questions

What is double NAT?
Double NAT happens when two routers both perform NAT (e.g. ISP modem-router plus your own router). Incoming connections get lost because the second router does not know where to forward them. Remove one router or put the second in bridge mode.'
Does UPnP fix NAT issues?
UPnP lets apps and games automatically open ports on the router. If your router supports it and the app uses it, enabling UPnP often fixes connection issues. Some routers have UPnP off by default.'
When should I use DMZ for gaming?
DMZ forwards all incoming ports to one device. It can fix strict NAT but exposes that device to the internet. Use only for a gaming console you trust, and only if port forwarding did not work.'

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