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LAN Play

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digdat0 edited this page Oct 30, 2026 · 1 revision

Mario Kart: Double Dash!! has a LAN mode: GameCubes with Broadband Adapters, linked by cables, each simulating the same race. MKDD-NX plays that same mode over Wi-Fi. Each Switch acts as if it had an adapter, and the game's network traffic goes between the consoles over your Wi-Fi network. No cables, adapters or PC are needed.

What you need

  • Two or more Switches running MKDD-NX 1.7.0 or later, all the same version.
  • All on the same Wi-Fi network (the same router). 5 GHz Wi-Fi near the router works best.
  • The standard game on every console: Level pack OFF on the − menu's Mods page.
    • Retro Track Grand Prix and its Baby Mode and Classic versions can't use LAN mode: their LAN entry runs code the mod loads from the disc, which MKDD-NX doesn't have.
    • MKDD Plus hasn't been tested.

Set up

On each Switch:

  1. Press −, open Multiplayer, and set LAN play to ON (left / right), or press A for the LAN play page.
  2. Choose Restart now on the LAN play page (it appears while a change waits for a restart). The game starts again.
  3. On the title screen, pick Wi-Fi mode (the game's LAN mode). Then follow the game's own screens: one console sets up the race and the others join it.

The game's LAN dialogs are reworded for the Switch ("Wi-Fi mode", "Nintendo Switch", the + Button).

The LAN play page

Row
LAN play ON / OFF. Applies after a restart
LAN peer ANY (default): consoles find each other by themselves. Or the other console's address (a.b.c.d, or a.b.c.d:port): press A to type it; left / right goes back to ANY. The row's hint shows this console's address, to type on the other one. Applies after a restart
Connection the link once Wi-Fi mode has started: LOOKING..., then N FOUND, XX MS (consoles found, round trip). Its hint gives the worst round trip and the share of lost packets
Restart now only while a change waits for a restart

With FPS counter on (Debug), the counter also shows the Wi-Fi link during LAN play, in yellow when it's poor.

During LAN play

  • Every console plays the same game. From the first Wi-Fi mode screen until the app restarts, MKDD-NX's gameplay changes are off on every console: the cheats (mini-turbos, perfect starts, special items), laps, any kart, the jump button, and computer karts in Wi-Fi battles. Every console simulates every kart from the players' inputs alone, so any difference would make the races drift apart.
  • Pause: + in a race opens the pause screen with Continue and Quit, as in a Grand Prix, but the race carries on behind it (it can't stop for one console). Quit leaves the session and goes back to the title screen; the other consoles see you leave.
  • The − menu doesn't pause the game either. Close it quickly in a race.
  • Custom characters show only on your own console; the other consoles see the character it plays as.
  • If a console stops (HOME menu, sleep, closing the app, Wi-Fi lost), the others give up after about 20 seconds.

Troubleshooting

What you see What to do
Connection stays at LOOKING... The consoles aren't on the same network, or the network blocks broadcasts (guest networks, some office or school Wi-Fi, "AP isolation" on a router). Set LAN peer on one console to the other's address (shown on the LAN peer row's hint), restart, and try again. If it still finds nothing, the network blocks traffic between devices: try another network, or a phone hotspot both Switches join.
N FOUND with no time The other console runs an older MKDD-NX. Update both to the same version.
"Data could not be properly transferred" The consoles stopped agreeing on the race: different versions or level packs, or the Wi-Fi dropped too much. Check both run the same version with Level pack OFF, then move nearer the router or use 5 GHz.
High round trip or lost packets in the hint Move nearer the router, use 5 GHz, or reduce other traffic on the network.
Wi-Fi mode missing from the title screen LAN play is OFF, the change waits for Restart now, or a Retro Track Grand Prix level pack is on.

For a bug report, set Logging to GAME (Debug) on each console before playing, and attach every console's logs/ folder (see Reporting bugs). The eth: and lan: lines show what the link did.

How it works

The game's own network code (its IP stack, LAN discovery and race sync) runs unchanged. Only the adapter driver under it is replaced. Each Ethernet frame the game sends goes to the other consoles as one UDP packet on port 51900, by broadcast and to the LAN peer when one is set. A frame for one console is sent twice, since Wi-Fi loses packets and the game's lockstep stalls on a lost one; the second copy is dropped as a repeat. Packets from a different game version are ignored. Each console gets its network address straight away from a small built-in DHCP server, instead of waiting 30 seconds for the game's fallback.

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