How to Add and Manage Linux Network Routes for Different Subnets

Two subnets (0 and 2) are connected via Router 1 and Router 2; to enable direct communication between them you must add appropriate routes on Linux.

The basic syntax of the Linux route command is:

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

Key options:

add : add a routing rule

del : delete a routing rule

-net : target is a network

-host : target is a single host

target : destination network or host

netmask : network mask for the destination

gw : gateway through which packets are sent

dev : network interface to use

1. Adding a Host Route

To allow host 192.168.2.10 to ping 192.168.0.8 via Router 2, add the following route on the source host:

route add -host 192.168.0.8 gw 192.168.2.1 dev eth0

This directs all traffic for 192.168.0.8 through gateway 192.168.2.1. Use route -n to view the entry. Delete it with:

route del 192.168.0.8

2. Adding a Network Route

Instead of adding a host route for each device, add a network route to reach the entire 0‑segment:

route add -net 192.168.0.0 netmask 255.255.255.0 gw 192.168.2.1 dev eth0

This routes all traffic for the 192.168.0.0/24 network via the same gateway. Verify with route -n. Remove it with:

route del -net 192.168.0.0/24 gw 192.168.2.1

3. Adding a Default Route

To enable a host in the 2‑segment to reach any other network, set a default route: route add default gw 192.168.2.1 dev eth0 This forwards all non‑local traffic through 192.168.2.1. Delete the default route with: route del default Routing table fields explained:

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

Gateway : next‑hop address; 0.0.0.0 means direct connection

Genmask : subnet mask (e.g., 255.255.255.255 for host, 0.0.0.0 for default)

Flags : U (up), G (gateway), H (host), R (reinstate), D (dynamic), M (modified), ! (reject)

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

Ref and Use : reference and usage counts (not used by Linux kernel)

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

Images illustrating the routing tables and commands:

Original article: https://www.cnblogs.com/YYFaGe/p/16599675.html (copyright belongs to the original author).