tutorials:add_network_routes [robotwiki]

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===== Add network routes =====

Sometimes a route needs to be manually configured in order to reach network nodes behind gateways/firewalls.

To do this you specify that to reach a certain subnet you need to go through a certain gateway.

In the following sections ''$SUBNET'' should be replaced with subnet (ip range) using either CIDR notation or subnet mask.

''$GATEWAY'' should be replaced with gateway's IP address.

These instructions assume that you are using IPv4 addresses.

==== Subnet syntax ====

=== CIDR notation ===

From: [[wp>Subnetwork]].

> The routing prefix may be expressed in Classless Inter-Domain Routing (CIDR) notation written as the first address of a network, followed by a slash character (/), and ending with the bit-length of the prefix. For example, 198.51.100.0/24 is the prefix of the Internet Protocol version 4 network starting at the given address, having 24 bits allocated for the network prefix, and the remaining 8 bits reserved for host addressing. Addresses in the range 198.51.100.0 to 198.51.100.255 belong to this network, with 198.51.100.255 as the subnet broadcast address. The IPv6 address specification 2001:db8::/32 is a large address block with 296 addresses, having a 32-bit routing prefix.

=== Subnet mask ===

From: [[wp>Subnetwork]].

> For IPv4, a network may also be characterized by its subnet mask or netmask, which is the bitmask that, when applied by a bitwise AND operation to any IP address in the network, yields the routing prefix. Subnet masks are also expressed in dot-decimal notation like an IP address. For example, the prefix 198.51.100.0/24 would have the subnet mask 255.255.255.0. 

==== Windows ====

Use [[#subnet_mask|subnet mask]], $SUBNET should be the route with 0 replacing variable parts of the IP. E.g. 192.168.X.0.

  - Open administrative shell: Press Alt+X and select "Command Prompt (Admin)"/"Windows Powershell (Admin)".
  - Run ''route -p ADD $SUBNET MASK $SUBNET_MASK $GATEWAY'' (the switch ''-p'' makes the route persistent)

==== Mac ====

Use [[#cidr_notation|CIDR notation]].

  - Open a terminal
  - Run ''sudo route -n add -net $SUBNET $GATEWAY''

==== Linux ====

Use [[#cidr-notation|CIDR notation]].

=== Temporarily via ip route (Most distros) ===
  - Open a terminal.
  - Find your preferred device using ''ip link'' (enp* or eth* for ethernet and wlp* or wifi* for wireless)
  - Store choosen interface by running ''DEVICE=enpXsY''

''sudo ip route add $SUBNET via $GATEWAY dev "$DEVICE"''

=== NetworkManager persistent (Most distros) ===

  - Open a terminal.
  - Find your preferred connection using ''nmcli connection show'' (e.g. ''Wired Connection 1''
  - Store choosen interface by running ''CONNECTION="Wired Connection 1"''

''sudo nmcli connection modify "$CONNECTION" +ipv4.routes "$SUBNET $GATEWAY"''

=== Netplan persistent route (Ubuntu/cloud init) ===

  - Open a terminal.
  - Find your preferred device using ''ip link'' (enp* or eth* for ethernet and wlp* or wifi* for wireless).
  - Replace enpXsY in YAML snippet below with chosen device.

Add the following to ''/etc/netplan/new_route.yaml'' (needs to be edited with sudo, any file name is fine with extension yaml/yml)

<code yaml>
network:
  version: 2
  ethernets:
    enpXsY:
      routes:
      - to: $SUBNET
        via: $GATEWAY
</code>

Then run ''sudo netplan apply''.