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jmgilman merged 1 commit into from
Oct 26, 2026
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docs(networking): document tag:dntls isolation rules #61

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20 changes: 19 additions & 1 deletion docs/docs/reference/networking/tailscale-policy.md
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Expand Up @@ -44,7 +44,7 @@ and trailing commas. Section syntax is documented in Tailscale's
| `tag:subnet-router` | Devices that advertise lab and home subnet routes into the tailnet | `autogroup:admin` |
| `tag:sandbox` | Sandbox hosts that accept advertised lab subnet routes | `autogroup:admin` |
| `tag:agentcompute` | Durable agentcompute HTTPS service | `autogroup:admin` |
| `tag:dntls` | `dntls` hosts; no tag-specific access rules, so only the `autogroup:admin` → `*:*` rule reaches them | `autogroup:admin` |
| `tag:dntls` | `dntls` hosts, isolated to each other, Studio, and the MacBook | `autogroup:admin` |

A tagged device is owned by its tag, not by the user who registered it. Removing
a tag from the policy while a device still carries it leaves that device without
Expand Down Expand Up @@ -93,6 +93,24 @@ service-to-other-host SSH, and sandbox-to-Studio SSH. OpenSSH separately
source-pins the service key; see the
[Studio authorization runbook](../../runbooks/agentcompute-studio-ssh.md).

`tag:dntls` hosts reach each other, Studio, and the MacBook on any port, and
nothing else in the tailnet:

| Source | Destination | Protocol | Port |
| --- | --- | --- | --- |
| `tag:dntls` | `tag:dntls` | Any | Any |
| `tag:dntls` | `studio-1` (`100.122.142.76`), `studio-1-v6` (`fd7a:115c:a1e0::be39:8e4c`) | Any | Any |
| `tag:dntls` | `macbook-pro` (`100.123.79.63`), `macbook-pro-v6` (`fd7a:115c:a1e0::e701:4f3f`) | Any | Any |

Like `studio-1`, the `macbook-pro` aliases name a user-owned device; do not
retag the MacBook. The `-v6` aliases admit each device's tailnet IPv6 address;
MagicDNS names resolve to IPv4 only. Policy tests allow peer, Studio, and
MacBook ports over both address families and deny an address adjacent to the
MacBook, the other tags, the Incus cluster API, and routed lab and home hosts.
Because routed lab addresses are denied, dntls hosts cannot use the split-DNS
resolver `10.10.10.1` for `glab.lol` and `lab.gilman.io`. Admin-owned devices
still reach dntls hosts through `autogroup:admin` → `*:*`.

## Credentials

CI authenticates with a Tailscale
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