Nintendo Switch Error Code 2123-1502 — What It Means & How to Fix It

What Does This Error Mean?

Error 2123-1502 means your Nintendo Switch cannot establish a proper connection for online play. This is a NAT (Network Address Translation) error — your router is too restrictive and is blocking the connections Nintendo's games need. It affects online multiplayer and peer-to-peer connections with other players.

Affected Models

Nintendo Switch
Nintendo Switch Lite
Nintendo Switch OLED

Common Causes

Your router's NAT type is set to C or D, which is too restrictive for Nintendo's online services
UPnP (Universal Plug and Play) is disabled on your router
Your internet provider uses Carrier-Grade NAT, which adds an extra layer of restrictions
A firewall or parental control setting on your router is blocking game traffic
Multiple routers or a router behind a modem in your home create a 'double NAT' situation

How to Fix It

Check your NAT type. Go to System Settings > Internet > Test Connection on your Switch. Wait for the full test to complete and note the NAT Type result shown at the bottom.

NAT Type A is ideal. Type B works. Type C or D causes this error and needs to be improved.
Enable UPnP on your router. Open a web browser on your computer or phone, go to your router's settings page (usually 192.168.1.1 or 192.168.0.1), and look for 'UPnP' under Advanced or Network settings. Enable it.

UPnP allows your Switch to automatically request the ports it needs. This is the easiest fix for most users.
Restart your router after enabling UPnP. Unplug it for 30 seconds, plug it back in, then retest on your Switch.

Changes to router settings usually require a restart to take effect.
Set up port forwarding for Nintendo Switch as an alternative to UPnP. Forward UDP ports 1 to 65535 and TCP ports 6667, 12400, 28910, 29900, 29901, and 29920 to your Switch's local IP address.

Port forwarding is more reliable than UPnP but takes more steps to configure. Nintendo's support website has a detailed guide.
Assign a static local IP address to your Switch. In your router's DHCP settings, reserve a fixed IP address for your Switch's MAC address. This ensures port forwarding rules always apply to the correct device.

Without a fixed IP, your Switch may get a different IP address after a restart and break your port forwarding rules.

When to Call a Professional

Error 2123-1502 is a network configuration issue, not a hardware fault. If you are not comfortable adjusting router settings, your internet provider's customer service can often walk you through enabling UPnP. For Carrier-Grade NAT, your provider may be able to assign you a static public IP address for a small monthly fee.

Frequently Asked Questions

What is NAT and why does it matter for gaming?

NAT stands for Network Address Translation. It is how your home router manages traffic between your devices and the internet. When NAT is too strict, it blocks incoming connections that multiplayer games need to work. Think of it like a strict mail room that refuses to accept certain deliveries — online gaming requires open two-way communication.

What is 'double NAT' and how do I know if I have it?

Double NAT happens when you have two routers connected in series — for example, a modem-router combo from your internet provider plus your own Wi-Fi router. Each device does its own NAT, which creates strict restrictions for gaming traffic. You can detect it by checking if your Switch shows a local IP starting with 192.168.x.x and then checking your router's WAN IP is also a 192.168.x.x address. The fix is to put the first device (the provider's modem-router) into 'bridge mode' or 'DMZ mode.'

Is it safe to enable UPnP on my router?

UPnP is generally safe for home users and is enabled by default on most routers. It allows devices on your network to automatically request the connections they need. For extra security, you can disable UPnP after your gaming session and re-enable it as needed. For most households, leaving it enabled is fine.