juanfont.headscale/docs/ref/routes.md

Routes

Headscale supports route advertising and can be used to manage subnet routers and exit nodes for a tailnet.

• Subnet routers may be used to connect an existing network such as a virtual private cloud or an on-premise network with your tailnet. Use a subnet router to access devices where Tailscale can't be installed or to gradually rollout Tailscale.
• Exit nodes can be used to route all Internet traffic for another Tailscale node. Use it to securely access the Internet on an untrusted Wi-Fi or to access online services that expect traffic from a specific IP address.

Subnet router

The setup of a subnet router requires double opt-in, once from a subnet router and once on the control server to allow its use within the tailnet. Optionally, use autoApprovers to automatically approve routes from a subnet router.

Setup a subnet router

Configure a node as subnet router

Register a node and advertise the routes it should handle as comma separated list:

$ sudo tailscale up --login-server <YOUR_HEADSCALE_URL> --advertise-routes=10.0.0.0/8,192.168.0.0/24

If the node is already registered, it can advertise new routes or update previously announced routes with:

$ sudo tailscale set --advertise-routes=10.0.0.0/8,192.168.0.0/24

Finally, enable IP forwarding to route traffic.

Enable the subnet router on the control server

The routes of a tailnet can be displayed with the headscale nodes list-routes command. A subnet router with the hostname myrouter announced the IPv4 networks 10.0.0.0/8 and 192.168.0.0/24. Those need to be approved before they can be used.

$ headscale nodes list-routes
ID | Hostname | Approved | Available                  | Serving
1  | myrouter |          | 10.0.0.0/8, 192.168.0.0/24 |

Approve all desired routes of a subnet router by specifying them as comma separated list:

$ headscale nodes approve-routes --identifier 1 --routes 10.0.0.0/8,192.168.0.0/24
Node updated

The node myrouter can now route the IPv4 networks 10.0.0.0/8 and 192.168.0.0/24 for the tailnet.

$ headscale nodes list-routes
ID | Hostname | Approved                   | Available                  | Serving
1  | myrouter | 10.0.0.0/8, 192.168.0.0/24 | 10.0.0.0/8, 192.168.0.0/24 | 10.0.0.0/8, 192.168.0.0/24

Use the subnet router

To accept routes advertised by a subnet router on a node:

$ sudo tailscale set --accept-routes

Please refer to the official Tailscale documentation for how to use a subnet router on different operating systems.

Restrict the use of a subnet router with ACL

The routes announced by subnet routers are available to the nodes in a tailnet. By default, without an ACL enabled, all nodes can accept and use such routes. Configure an ACL to explicitly manage who can use routes.

The ACL snippet below defines three hosts, a subnet router router, a regular node node and service.example.net as internal service that can be reached via a route on the subnet router router. The first ACL rule allows anyone to see the subnet router router without allowing access to any service of the subnet router itself. The second ACL rule allows the node node to access service.example.net on port 80 and 443 which is reachable via the subnet router.

{
  "hosts": {
    "router": "100.64.0.1/32",
    "node": "100.64.0.2/32",
    "service.example.net": "192.168.0.1/32"
  },
  "acls": [
    {
      "action": "accept",
      "src": [
        "*"
      ],
      "dst": [
        "router:0"
      ]
    },
    {
      "action": "accept",
      "src": [
        "node"
      ],
      "dst": [
        "service.example.net:80,443"
      ]
    }
  ]
}

Automatically approve routes of a subnet router

The initial setup of a subnet router usually requires manual approval of their announced routes on the control server before they can be used by a node in a tailnet. Headscale supports the autoApprovers section of an ACL to automate the approval of routes served with a subnet router.

The ACL snippet below defines a group group:routers with one user user as member. This group owns the tag tag:router which is used for routes in the autoApprovers section. The IPv4 route 192.168.0.0/24 is automatically approved when announced by a new subnet router which is owned by the group group:routers and that also advertises the tag tag:router.

{
  "groups": {
    "group:routers": [
      "user@"
    ]
  },
  "tagOwners": {
    "tag:router": [
      "group:routers"
    ]
  },
  "autoApprovers": {
    "routes": {
      "192.168.0.0/24": [
        "tag:router"
      ]
    }
  },
  "acls": [
    // more rules
  ]
}

Advertise the route 192.168.0.0/24 from a subnet router that also advertises the tag tag:router when joining the tailnet:

$ sudo tailscale up --login-server <YOUR_HEADSCALE_URL> --advertise-tags tag:router --advertise-routes 192.168.0.0/24

Please see the official Tailscale documentation for more information on auto approvers.

Exit node

The setup of an exit node requires double opt-in, once from an exit node and once on the control server to allow its use within the tailnet. Optionally, use autoApprovers to automatically approve an exit node.

Setup an exit node

Configure a node as exit node

Register a node and make it advertise itself as an exit node:

$ sudo tailscale up --login-server <YOUR_HEADSCALE_URL> --advertise-exit-node

If the node is already registered, it can advertise exit capabilities like this:

$ sudo tailscale set --advertise-exit-node

Finally, enable IP forwarding to route traffic.

Enable the exit node on the control server

The routes of a tailnet can be displayed with the headscale nodes list-routes command. An exit node can be recognized by its announced routes: 0.0.0.0/0 for IPv4 and ::/0 for IPv6. The exit node with the hostname myexit is already available, but needs to be approved:

$ headscale nodes list-routes
ID | Hostname | Approved | Available       | Serving
1  | myexit   |          | 0.0.0.0/0, ::/0 |

For exit nodes, it is sufficient to approve either the IPv4 or IPv6 route. The other will be approved automatically.

$ headscale nodes approve-routes --identifier 1 --routes 0.0.0.0/0
Node updated

The node myexit is now approved as exit node for the tailnet:

$ headscale nodes list-routes
ID | Hostname | Approved        | Available       | Serving
1  | myexit   | 0.0.0.0/0, ::/0 | 0.0.0.0/0, ::/0 | 0.0.0.0/0, ::/0

Use the exit node

The exit node can now be used on a node with:

$ sudo tailscale set --exit-node myexit

Please refer to the official Tailscale documentation for how to use an exit node on different operating systems.

Restrict the use of an exit node with ACL

An exit node is offered to all nodes in a tailnet. By default, without an ACL enabled, all nodes in a tailnet can select and use an exit node. Configure autogroup:internet in an ACL rule to restrict who can use any of the available exit nodes.

{
  "acls": [
    {
      "action": "accept",
      "src": [
        "..."
      ],
      "dst": [
        "autogroup:internet:*"
      ]
    }
  ]
}

Automatically approve an exit node with auto approvers

The initial setup of an exit node usually requires manual approval on the control server before it can be used by a node in a tailnet. Headscale supports the autoApprovers section of an ACL to automate the approval of a new exit node as soon as it joins the tailnet.

The ACL snippet below defines a group group:exits with one user user as member. This group owns the tag tag:exit which is used for exitNode in the autoApprovers section. A new exit node which is owned by the group group:exits and that also advertises the tag tag:exit is automatically approved:

{
  "groups": {
    "group:exits": [
      "user@"
    ]
  },
  "tagOwners": {
    "tag:exit": [
      "group:exits"
    ]
  },
  "autoApprovers": {
    "exitNode": [
      "tag:exit"
    ]
  },
  "acls": [
    // more rules
  ]
}

Advertise a node as exit node and also advertise the tag tag:exit when joining the tailnet:

$ sudo tailscale up --login-server <YOUR_HEADSCALE_URL> --advertise-tags tag:exit --advertise-exit-node

Please see the official Tailscale documentation for more information on auto approvers.

High availability

Headscale has limited support for high availability routing. Multiple subnet routers with overlapping routes or multiple exit nodes can be used to provide high availability for users. If one router node goes offline, another one can serve the same routes to clients. Please see the official Tailscale documentation on high availability for details.

!!! bug

In certain situations it might take up to 16 minutes for Headscale to detect a node as offline. A failover node
might not be selected fast enough, if such a node is used as subnet router or exit node causing service
interruptions for clients. See [issue 2129](https://github.com/juanfont/headscale/issues/2129) for more information.

Troubleshooting

Enable IP forwarding

A subnet router or exit node is routing traffic on behalf of other nodes and thus requires IP forwarding. Check the official Tailscale documentation for how to enable IP forwarding.