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.
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.
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.