DERP relay usage detected instead of direct connections

Traffic is being routed through DERP relay servers instead of direct peer-to-peer connections, visible in tailscale status output as 'relay "code"'

Check tailscale status output for relay indicators. Use tailscale ping to test if direct path can be established. Investigate firewall rules, NAT configuration, or network topology preventing direct connections. Review which firewall ports need to be opened.