Static Routes -RedHat Linux

Adding Temporary Static Routes

The route add command can be used to add new routes to your server that will last till the next reboot. It has the advantage of being univeral to all versions of Linux and is well documented in the man pages. In our example the reference to the 10.0.0.0 network has to be preceded with a -net switch and the subnet mask and gateway values also have to be preceded by the netmask and gw switches respectively.

[root@bigboy tmp]# route add -net 10.0.0.0 netmask 255.0.0.0 gw 192.168.1.254 eth0

If you wanted to add a route to an individual server, then the "-host" switch would be used with no netmask value. (The route command automatically knows the mask should be 255.255.255.255). Here is an example for a route to host 10.0.0.1.

[root@bigboy tmp]# route add -host 10.0.0.1 gw 192.168.1.254 eth0

A universal way of making this change persistent after a reboot would be to place this route add command in the file /etc/rc.d/rc.local, which is always run at the end of the booting process.

Adding Permanent Static Routes

In Fedora Linux, permanent static routes are added on a per interface basis in files located in the /etc/sysconfig/network-scripts directory. The filename format is route-interface-name so the filename for interface wlan0 would be route-wlan0.

The format of the file is quite intuitive with the target network coming in the first column followed by the word via and then the gateway's IP address. In our routing example, to set up a route to network 10.0.0.0 with a subnet mask of 255.0.0.0 (a mask with the first 8 bits set to 1) via the 192.168.1.254 gateway, we would have to configure file /etc/sysconfig/network-scripts/route-eth0 to look like this:

#

# File /etc/sysconfig/network-scripts/route-wlan0

#

10.0.0.0/8 via 192.168.1.254

Note: The /etc/sysconfig/network-scripts/route-* filename is very important. Adding the wrong interface extension at the end will result in the routes not being added after the next reboot. There will also be no reported errors on the screen or any of the log files in the /var/log/ directory.

You can test the new file by running the /etc/sysconfig/network-scripts/ifup-routes command with the interface name as the sole argument. In the next example we check the routing table to see no routes to the 10.0.0.0 network and execute the ifup-routes command, which then adds the route:

How to Delete a Route

Here's how to delete the routes added in the previous section.

[root@bigboy tmp]# route del -net 10.0.0.0 netmask 255.0.0.0 gw 192.168.1.254 wlan0

The file /etc/sysconfig/network-scripts/route-wlan0 will also have to be updated so that when you reboot the server will not reinsert the route. Delete the line that reads:

10.0.0.0/8 via 192.168.1.254