How to Add Host, Network, and Default Routes in Linux Using the route Command

Understanding Linux Routing Commands

Linux uses the route command to add or delete routing entries, allowing communication between different subnets.

Command Syntax

route [add|del] [-net|-host] target [netmask Nm] [gw Gw] [[dev] If]

add : add a routing rule

del : delete a routing rule

-net : target is a network

-host : target is a host

target : destination network or host

netmask : network mask of the destination

gw : gateway through which packets are sent

dev : network interface

1. Adding a Host Route

To enable host 192.168.2.10 to ping host 192.168.0.8 via router 2, add the following rule on the source host: route add -host 192.168.0.8 gw 192.168.2.1 dev eth0 This directs traffic for 192.168.0.8 to the gateway 192.168.2.1. Use route to verify the entry.

2. Adding a Network Route

When a host needs to reach an entire subnet, add a network route instead of individual host routes:

route add -net 192.168.0.0 netmask 255.255.255.0 gw 192.168.2.1 dev eth0

This routes all traffic to the 0‑segment through the same gateway. The routing table shows the entry with appropriate flags.

3. Adding a Default Route

To forward all non‑local traffic to a default gateway, use: route add default gw 192.168.2.1 dev eth0 The default route directs any destination outside the 2‑segment to the specified gateway.

Routing Table Fields Explained

Destination : target network or host; 0.0.0.0 denotes the default gateway.

Gateway : address of the gateway; 0.0.0.0 means the destination is on the same subnet.

Genmask : netmask for the destination; 255.255.255.255 for a host, 0.0.0.0 for default.

Flags : indicators such as U (up), G (gateway), H (host), R (reinstated), D (dynamic), M (modified), ! (reject).

Metric : route distance (used in large LAN/WAN).

Iface : network interface name, e.g., eth0.

To remove routes, use route del with the same parameters, e.g., route del 192.168.0.8, route del -net 192.168.0.0/24 gw 192.168.2.1, or route del default.