Direct Connection Latency Fix

Direct Connection Latency Fix | Generated by AI

Home 2026.06

Result: SSH Latency 5–6s → 1.9s

What Changed

Tailscale switched from DERP relay to a direct peer-to-peer connection:

Before:  Mac → DERP relay (Singapore) → to       ~500ms RTT → 5–6s SSH
After:   Mac → direct <IP_ADDRESS>:<PORT> → to     76ms RTT  → 1.9s SSH

Root Cause

Both sides actually support direct connection:

to machine has cone NAT (MappingVariesByDestIP: false) — mappings are stable
Mac’s parents’ router has UPnP enabled — port mapping works

But Tailscale was giving up on NAT traversal probing too early and falling back to DERP relay. Running tailscale ping --until-direct forced it to keep probing until the direct path was found.

Making It Stick

Two options:

Option 1 — Periodic re-probe (quick fix)

# cron on Mac: re-establish direct every 10 min if it drops
*/10 * * * * tailscale ping --until-direct <TAILSCALE_HOSTNAME>

Option 2 — Router port forward (permanent fix) Forward UDP 41641 on home router (192.168.x.1 LuCI) → 192.168.x.36. This makes to always directly reachable, so Tailscale finds the direct path instantly without needing to probe.

Option 2 is the clean fix — one config change, no cron dependency.

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