{"slug":"troubleshoot-tcp-connection-issues-between-two-devices","title":"Troubleshoot TCP connection issues between two devices","tags":["tailscale","networking","devices"],"agent_summary":"Last validated: Mar 16, 2026","trigger_phrases":[],"runnable":false,"markdown":"\r\n# Troubleshoot TCP connection issues between two devices\r\n\r\nLast validated: Mar 16, 2026\r\n\r\nIf your devices are visible in the admin console, and there is no [access rule](https://tailscale.com/docs/reference/syntax/policy-file#access-rules) blocking connections between the devices, check the level of connectivity with Tailscale's three types of `ping`:\r\n\r\n- `ping 100.x.x.x` tells the OS to send an ICMP ping across the tailnet.\r\n- `tailscale ping 100.x.x.x` tests whether the two `tailscaled` processes can communicate at all, and how (direct, or relayed).\r\n- `tailscale ping --tsmp 100.x.x.x` sends a packet that goes one level further than `tailscale ping`, also going through the WireGuard level, but doesn't involve the host's networking stack.\r\n\r\nPacket size limits can also cause connection problems on certain types of networks.\r\n\r\nTailscale uses a maximum transmission unit (MTU) of `1280`. If there are other interfaces which might send a packet larger than this, those packets might get dropped silently. These can be verified by using `tcpdump`.\r\n\r\nTo solve this, we can set the MTU at the LAN level to a lower value, or use MSS (maximum segment size) clamping.\r\n\r\n![Project Logo](https://cdn.brandfetch.io/tailscale.com/fallback/lettermark/theme/dark/h/256/w/256/icon?c=1bfwsmEH20zzEfSNTed)\r\n\r\nAsk AI\r\n\r\nreCAPTCHA\r\n\r\nRecaptcha requires verification.\r\n\r\nprotected by **reCAPTCHA**\r\n","html":"<h1>Troubleshoot TCP connection issues between two devices</h1>\n<p>Last validated: Mar 16, 2026</p>\n<p>If your devices are visible in the admin console, and there is no <a href=\"https://tailscale.com/docs/reference/syntax/policy-file#access-rules\">access rule</a> blocking connections between the devices, check the level of connectivity with Tailscale's three types of <code>ping</code>:</p>\n<ul>\n<li><code>ping 100.x.x.x</code> tells the OS to send an ICMP ping across the tailnet.</li>\n<li><code>tailscale ping 100.x.x.x</code> tests whether the two <code>tailscaled</code> processes can communicate at all, and how (direct, or relayed).</li>\n<li><code>tailscale ping --tsmp 100.x.x.x</code> sends a packet that goes one level further than <code>tailscale ping</code>, also going through the WireGuard level, but doesn't involve the host's networking stack.</li>\n</ul>\n<p>Packet size limits can also cause connection problems on certain types of networks.</p>\n<p>Tailscale uses a maximum transmission unit (MTU) of <code>1280</code>. If there are other interfaces which might send a packet larger than this, those packets might get dropped silently. These can be verified by using <code>tcpdump</code>.</p>\n<p>To solve this, we can set the MTU at the LAN level to a lower value, or use MSS (maximum segment size) clamping.</p>\n<p><img src=\"https://cdn.brandfetch.io/tailscale.com/fallback/lettermark/theme/dark/h/256/w/256/icon?c=1bfwsmEH20zzEfSNTed\" alt=\"Project Logo\"></p>\n<p>Ask AI</p>\n<p>reCAPTCHA</p>\n<p>Recaptcha requires verification.</p>\n<p>protected by <strong>reCAPTCHA</strong></p>\n"}