Linux route Add Command Examples

I am a new Linux user. How do I add a new or default gateway using route command on Linux operating systems? How can I use route command to show or set a new route on Linux based server or desktop system?

In Linux and Unix-like system, a gateway is nothing but device that connects two networks. Often it is called a router or gateway. In most cases your ISP’s modem act as a default router or gateway. You can use any one of the following tool to add, display, delete Linux kernel routing table:

1. route command : show / manipulate the IP routing table on Linux.
2. ip command : show / manipulate routing, devices, policy routing and tunnels on Linux.

Display your current routing table

Open the Terminal or login to server using ssh/console. Type the following command to display routing table:
# route
OR
# route -n
Sample outputs:

# ip route show
OR
# ip route list
Sample outputs:

Linux route Add Command Examples

I am going to show you both ip and route command. Most modern Linux distro recommend and use the ip command for setting or displaying default gateway IP address on Linux. Let us see some examples.

Linux add a default route using route command

Route all traffic via 192.168.1.254 gateway connected via eth0 network interface:
# route add default gw 192.168.1.254 eth0

Linux add a default gateway (route) using ip command

Route all traffic via 192.168.1.254 gateway connected via eth0 network interface:
# ip route add 192.168.1.0/24 dev eth0

Verify newly added route ip in the Linux kernel routing table

To verify new routing table, enter:
# ip route list
OR
# route -n

Verify new route

Use the ping command to verify connectivity to your router or external network:
# ping your-router-ip-here
# ping your-ISPs-Gateway-ip-here
# ping 192.168.1.254
# ping www.cyberciti.biz
You should able to ping public IP address too:
ping 1.1.1.1
ping 8.8.8.8
And use the dig command or host command to resolve domain names provided that /etc/resolv.conf configured with correct DNS server names:
host www.cyberciti.biz
host google.com
dig www.cyberciti.biz

How do I make routing changes persistent across reboots?

To make route entry persistent in the Linux kernel routing table, you need to modify config file as per your Linux distributions.

RHEL/CentOS/Fedora/Scientific Linux persistent routing configuration

Edit /etc/sysconfig/network and set default gateway IP address:
# vi /etc/sysconfig/network
Sample outputs:

You can add additional static route for eth0 by editing /etc/sysconfig/network-scripts/route-eth0 file as follows:

10.0.0.0/8 via 10.10.29.65

The above config sets static routing for network 10.0.0.0/8 via 10.9.38.65 router.

Debian / Ubuntu Linux persistence static routing configuration

Edit /etc/network/interfaces file, enter:
# vi /etc/network/interfaces
Append the following in eth0 section:

up route add -net 192.168.1.0 netmask 255.255.255.0 gw 192.168.1.254
down route del -net 192.168.1.0 netmask 255.255.255.0 gw 192.168.1.254

Save and close the file.

Generic method to add persistent static routing on Linux

The following method works with almost all Linux distributions.

Edit /etc/rc.d/rc.local or /etc/rc.local, enter
# vi /etc/rc.local
Append the following line:

/sbin/ip route add 192.168.1.0/24 dev eth0

OR

/sbin/ip route add 192.168.1.0/24 dev eth0

Save and close the file in vim text editor.

Recommended readings

• Configure Static Routes In Debian or Red Hat Enterprise Linux

Fonte: https://www.cyberciti.biz/faq/linux-route-add/