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

Two subnets (0.0.0.0/24 and 2.0.0.0/24) are connected by Router 1 (0‑net) and Router 2 (2‑net). To enable direct communication between hosts on different subnets, static routes must be added on the Linux hosts.

Route command syntax

The generic form of the Linux route command is:

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

add : create a new routing entry

del : remove an existing routing entry

-net : target is a network

-host : target is a single host

target : destination network or host address

netmask : subnet mask for the destination

gw : gateway through which packets are sent

dev : network interface to use (e.g., eth0)

1. Adding a host route

To allow host 192.168.2.10 to ping host 192.168.0.8 via Router 2, run 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. Verify with:

route -n

The routing table fields are:

Destination : target network or host (e.g., 0.0.0.0 for default gateway)

Gateway : gateway address; 0.0.0.0 means the destination is on the same LAN

Genmask : subnet mask (255.255.255.255 for a host, 0.0.0.0 for default)

Flags :

U – route is up

G – uses a gateway

H – target is a host

R – restored from a dynamic route

D – installed by a daemon

M – modified by a daemon

! – reject route

Metric : cost of the route (used in larger networks)

Ref and Use : internal kernel counters

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

To delete the host route:

route del 192.168.0.8

2. Adding a network route

If 192.168.2.10 needs to reach all hosts in the 0‑net, add a single network route on the host:

route add -net 192.168.0.0 netmask 255.255.255.0 gw 192.168.2.1 dev eth0

This tells the kernel that any address in 192.168.0.0/24 should be sent to gateway 192.168.2.1.

To delete the network route:

route del -net 192.168.0.0/24 gw 192.168.2.1

3. Adding a default route

To allow any traffic destined for networks other than the 2‑net to be forwarded via Router 2, set a default route:

route add default gw 192.168.2.1 dev eth0

The default route means all non‑local traffic is sent to 192.168.2.1. To remove it: route del default These commands enable precise control over inter‑subnet communication in Linux environments.