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 NAT gateway for a device with two network interfaces ( eth0 and eth1 ).

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:

vyos@vyos$ configure
vyos@vyos#

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

commit

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

save

• 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 Configuration Mode issue the following commands:

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 'LAN'

After switching to Configuration Mode issue the following commands, and your system will listen on every interface for incoming SSH connections. You might want to check the SSH chapter on how to listen on specific addresses only.

set service ssh port '22'

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

set service dhcp-server shared-network-name LAN subnet 192.168.0.0/24 option default-router '192.168.0.1'
set service dhcp-server shared-network-name LAN subnet 192.168.0.0/24 option name-server '192.168.0.1'
set service dhcp-server shared-network-name LAN subnet 192.168.0.0/24 option 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 dhcp-server shared-network-name LAN subnet 192.168.0.0/24 subnet-id '1'

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'

The following settings will configure SNAT rules for our internal/LAN network, allowing hosts to communicate through the outside/WAN network via IP masquerade.

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

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 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.

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.

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'

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

Using options defined in , 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:

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

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.

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:

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

Alternatively, you can take the more traditional stateful connection filtering approach by creating rules on each base hook’s chain:

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

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.

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 :

set firewall ipv4 input filter default-action 'drop'

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:

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:

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:

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'

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:

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:

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:

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

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:

set system login user myvyosuser authentication plaintext-password mysecurepassword

Set up Key Based Authentication :

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 SSH :

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

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

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!