.. _quick-start:

###########
Quick Start
###########

This chapter will guide you on how to get up to speed quickly using your new
VyOS system. It will show you a very basic configuration example that will
provide a :ref:`nat` gateway for a device with two network interfaces
(``eth0`` and ``eth1``).

.. _quick-start-configuration-mode:

Configuration Mode
##################

By default, VyOS is in operational mode, and the command prompt displays
a ``$``. To configure VyOS, you will need to enter configuration mode, resulting
in the command prompt displaying a ``#``, as demonstrated below:

.. code-block:: none

  vyos@vyos$ configure
  vyos@vyos#

Commit and Save
################

After every configuration change, you need to apply the changes by using the
following command:

.. code-block:: none

  commit

Once your configuration works as expected, you can save it permanently by using
the following command:

.. code-block:: none

  save

Interface Configuration
#######################

* Your outside/WAN interface will be ``eth0``. It will receive its interface
  address via DHCP.
* Your internal/LAN interface will be ``eth1``. It will use a static IP address
  of ``192.168.0.1/24``.

After switching to :ref:`quick-start-configuration-mode` issue the following
commands:

.. code-block:: none

  set interfaces ethernet eth0 address dhcp
  set interfaces ethernet eth0 description 'OUTSIDE'
  set interfaces ethernet eth1 address '192.168.0.1/24'
  set interfaces ethernet eth1 description 'INSIDE'


SSH Management
##############

After switching to :ref:`quick-start-configuration-mode` issue the following
commands, and your system will listen on every interface for incoming SSH
connections. You might want to check the :ref:`ssh` chapter on how to listen
on specific addresses only.

.. code-block:: none

  set service ssh port '22'


.. _dhcp-dns-quick-start:

DHCP/DNS quick-start
####################

The following settings will configure DHCP and DNS services on
your internal/LAN network, where VyOS will act as the default gateway and
DNS server.

* The default gateway and DNS recursor address will be ``192.168.0.1/24``
* The address range ``192.168.0.2/24 - 192.168.0.8/24`` will be reserved for
  static assignments
* DHCP clients will be assigned IP addresses within the range of
  ``192.168.0.9 - 192.168.0.254`` and have a domain name of ``internal-network``
* DHCP leases will hold for one day (86400 seconds)
* VyOS will serve as a full DNS recursor, replacing the need to utilize Google,
  Cloudflare, or other public DNS servers (which is good for privacy)
* Only hosts from your internal/LAN network can use the DNS recursor

.. code-block:: none

  set service dhcp-server shared-network-name LAN subnet 192.168.0.0/24 default-router '192.168.0.1'
  set service dhcp-server shared-network-name LAN subnet 192.168.0.0/24 name-server '192.168.0.1'
  set service dhcp-server shared-network-name LAN subnet 192.168.0.0/24 domain-name 'vyos.net'
  set service dhcp-server shared-network-name LAN subnet 192.168.0.0/24 lease '86400'
  set service dhcp-server shared-network-name LAN subnet 192.168.0.0/24 range 0 start '192.168.0.9'
  set service dhcp-server shared-network-name LAN subnet 192.168.0.0/24 range 0 stop '192.168.0.254'

  set service dns forwarding cache-size '0'
  set service dns forwarding listen-address '192.168.0.1'
  set service dns forwarding allow-from '192.168.0.0/24'


NAT
###

The following settings will configure :ref:`source-nat` rules for our
internal/LAN network, allowing hosts to communicate through the outside/WAN
network via IP masquerade.

.. code-block:: none

  set nat source rule 100 outbound-interface name 'eth0'
  set nat source rule 100 source address '192.168.0.0/24'
  set nat source rule 100 translation address masquerade

Firewall
########

A new firewall structure—which uses the ``nftables`` backend, rather
than ``iptables``—is available on all installations starting from
VyOS ``1.4-rolling-202308040557``. The firewall supports creation of distinct,
interlinked chains for each `Netfilter hook
<https://wiki.nftables.org/wiki-nftables/index.php/Netfilter_hooks>`_
and allows for more granular control over the packet filtering process.

The firewall begins with the base ``filter`` tables you define for each of the
``forward``, ``input``, and ``output`` Netfiter hooks. Each of these tables is
populated with rules that are processed in order and can jump to other chains
for more granular filtering.

Configure Firewall Groups
-------------------------

To make firewall configuration easier, we can create groups of interfaces,
networks, addresses, ports, and domains that describe different parts of
our network. We can then use them for filtering within our firewall rulesets,
allowing for more concise and readable configuration.

In this case, we will create two interface groups—a ``WAN`` group for our
interfaces connected to the public internet and a ``LAN`` group for the
interfaces connected to our internal network. Additionally, we will create a
network group, ``NET-INSIDE-v4``, that contains our internal subnet.

.. code-block:: none

  set firewall group interface-group WAN interface eth0
  set firewall group interface-group LAN interface eth1
  set firewall group network-group NET-INSIDE-v4 network '192.168.0.0/24'

Configure Stateful Packet Filtering
-----------------------------------

With the new firewall structure, we have have a lot of flexibility in how we
group and order our rules, as shown by the two alternative approaches below.

Option 1: Global State Policies
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
Using options defined in ``set firewall global-options state-policy``, state
policy rules that applies for both IPv4 and IPv6 are created. These global
state policies also applies for all traffic that passes through the router
(transit) and for traffic originated/destinated to/from the router itself, and
will be evaluated before any other rule defined in the firewall.

Most installations would choose this option, and will contain:

.. code-block:: none

  set firewall global-options state-policy established action accept
  set firewall global-options state-policy related action accept
  set firewall global-options state-policy invalid action drop

Option 2: Common/Custom Chain
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

We can create a common chain for stateful connection filtering of multiple
interfaces (or multiple netfilter hooks on one interface). Those individual
chains can then jump to the common chain for stateful connection filtering,
returning to the original chain for further rule processing if no action is
taken on the packet.

The chain we will create is called ``CONN_FILTER`` and has three rules:

- A default action of ``return``, which returns the packet back to the original
  chain if no action is taken.
- A rule to ``accept`` packets from established and related connections.
- A rule to ``drop`` packets from invalid connections.

.. code-block:: none

  set firewall ipv4 name CONN_FILTER default-action 'return'

  set firewall ipv4 name CONN_FILTER rule 10 action 'accept'
  set firewall ipv4 name CONN_FILTER rule 10 state established
  set firewall ipv4 name CONN_FILTER rule 10 state related

  set firewall ipv4 name CONN_FILTER rule 20 action 'drop'
  set firewall ipv4 name CONN_FILTER rule 20 state invalid

Then, we can jump to the common chain from both the ``forward`` and ``input``
hooks as the first filtering rule in the respective chains:

.. code-block:: none

  set firewall ipv4 forward filter rule 10 action 'jump'
  set firewall ipv4 forward filter rule 10 jump-target CONN_FILTER

  set firewall ipv4 input filter rule 10 action 'jump'
  set firewall ipv4 input filter rule 10 jump-target CONN_FILTER

Option 2: Per-Hook Chain
^^^^^^^^^^^^^^^^^^^^^^^^

Alternatively, instead of configuring the ``CONN_FILTER`` chain described above,
you can take the more traditional stateful connection filtering approach by
creating rules on each hook's chain:

.. code-block:: none

  set firewall ipv4 forward filter rule 5 action 'accept'
  set firewall ipv4 forward filter rule 5 state established
  set firewall ipv4 forward filter rule 5 state related
  set firewall ipv4 forward filter rule 10 action 'drop'
  set firewall ipv4 forward filter rule 10 state invalid

  set firewall ipv4 input filter rule 5 action 'accept'
  set firewall ipv4 input filter rule 5 state established
  set firewall ipv4 input filter rule 5 state related
  set firewall ipv4 input filter rule 10 action 'drop'
  set firewall ipv4 input filter rule 10 state invalid

Block Incoming Traffic
----------------------

Now that we have configured stateful connection filtering to allow traffic from
established and related connections, we can block all other incoming traffic
addressed to our local network.

Create a new chain (``OUTSIDE-IN``) which will drop all traffic that is not
explicitly allowed at some point in the chain. Then, we can jump to that chain
from the ``forward`` hook when traffic is coming from the ``WAN`` interface
group and is addressed to our local network.

.. code-block:: none

  set firewall ipv4 name OUTSIDE-IN default-action 'drop'

  set firewall ipv4 forward filter rule 100 action jump
  set firewall ipv4 forward filter rule 100 jump-target OUTSIDE-IN
  set firewall ipv4 forward filter rule 100 inbound-interface group WAN
  set firewall ipv4 forward filter rule 100 destination group network-group NET-INSIDE-v4

We should also block all traffic destinated to the router itself that isn't
explicitly allowed at some point in the chain for the ``input`` hook. As
we've already configured stateful packet filtering above, we only need to
set the default action to ``drop``:

.. code-block:: none

  set firewall ipv4 input filter default-action 'drop'

Allow Management Access
---------------------------

We can now configure access to the router itself, allowing SSH
access from the inside/LAN network and rate limiting SSH access from the
outside/WAN network.

First, create a new dedicated chain (``VyOS_MANAGEMENT``) for management
access, which returns to the parent chain if no action is taken. Add a rule
to accept traffic from the ``LAN`` interface group:

.. code-block:: none

  set firewall ipv4 name VyOS_MANAGEMENT default-action 'return'

Configure a rule on the ``input`` hook filter to jump to the ``VyOS_MANAGEMENT``
chain when new connections are addressed to port 22 (SSH) on the router itself:

.. code-block:: none

  set firewall ipv4 input filter rule 20 action jump
  set firewall ipv4 input filter rule 20 jump-target VyOS_MANAGEMENT
  set firewall ipv4 input filter rule 20 destination port 22
  set firewall ipv4 input filter rule 20 protocol tcp

Finally, configure the ``VyOS_MANAGEMENT`` chain to accept connection from the
``LAN`` interface group while limiting requests coming from the ``WAN``
interface group to 4 per minute:

.. code-block:: none

  set firewall ipv4 name VyOS_MANAGEMENT rule 15 action 'accept'
  set firewall ipv4 name VyOS_MANAGEMENT rule 15 inbound-interface group 'LAN'

  set firewall ipv4 name VyOS_MANAGEMENT rule 20 action 'drop'
  set firewall ipv4 name VyOS_MANAGEMENT rule 20 recent count 4
  set firewall ipv4 name VyOS_MANAGEMENT rule 20 recent time minute
  set firewall ipv4 name VyOS_MANAGEMENT rule 20 state new
  set firewall ipv4 name VyOS_MANAGEMENT rule 20 inbound-interface group 'WAN'

  set firewall ipv4 name VyOS_MANAGEMENT rule 21 action 'accept'
  set firewall ipv4 name VyOS_MANAGEMENT rule 21 state new
  set firewall ipv4 name VyOS_MANAGEMENT rule 21 inbound-interface group 'WAN'

Allow Access to Services
------------------------

Here we're allowing the router to respond to pings. Then, we can allow access to
the DNS recursor we configured earlier, accepting traffic bound for port 53 from
all hosts on the ``NET-INSIDE-v4`` network:

.. code-block:: none

  set firewall ipv4 input filter rule 30 action 'accept'
  set firewall ipv4 input filter rule 30 icmp type-name 'echo-request'
  set firewall ipv4 input filter rule 30 protocol 'icmp'
  set firewall ipv4 input filter rule 30 state new

  set firewall ipv4 input filter rule 40 action 'accept'
  set firewall ipv4 input filter rule 40 destination port '53'
  set firewall ipv4 input filter rule 40 protocol 'tcp_udp'
  set firewall ipv4 input filter rule 40 source group network-group NET-INSIDE-v4

Finally, we can now configure access to the services running on this router,
allowing all connections coming from localhost:

.. code-block:: none

  set firewall ipv4 input filter rule 50 action 'accept'
  set firewall ipv4 input filter rule 50 source address 127.0.0.0/8

Commit changes, save the configuration, and exit configuration mode:

.. code-block:: none

  vyos@vyos# commit
  vyos@vyos# save
  Saving configuration to '/config/config.boot'...
  Done
  vyos@vyos# exit
  vyos@vyos$

Hardening
#########

Especially if you are allowing SSH remote access from the outside/WAN
interface, there are a few additional configuration steps that should be taken.

Replace the default ``vyos`` system user:

.. code-block:: none

  set system login user myvyosuser authentication plaintext-password mysecurepassword

Set up :ref:`ssh_key_based_authentication`:

.. code-block:: none

  set system login user myvyosuser authentication public-keys myusername@mydesktop type ssh-rsa
  set system login user myvyosuser authentication public-keys myusername@mydesktop key contents_of_id_rsa.pub

Finally, try and SSH into the VyOS install as your new user. Once you have
confirmed that your new user can access your router without a password, delete
the original ``vyos`` user and completely disable password authentication for
:ref:`ssh`:

.. code-block:: none

  delete system login user vyos
  set service ssh disable-password-authentication

As above, commit your changes, save the configuration, and exit
configuration mode:

.. code-block:: none

  vyos@vyos# commit
  vyos@vyos# save
  Saving configuration to '/config/config.boot'...
  Done
  vyos@vyos# exit
  vyos@vyos$

You now should have a simple yet secure and functioning router to experiment
with further. Enjoy!