Adding a Default Route
Now we need to create the route itself. To do this dynamically, we can use the route command, just as we did for adding the routes between our subnets. But this time we use the “default” keyword to signify that this is the default route:
xenon# route add default 172.35.63.1 1 xenon#
Checking with netstat will show that the routes have now been created: the first to the network that the default route is connected to, and the second to the default router itself. It's always worth remembering that we must have a route to and from the default router!
xenon# netstat -rn Routing Table: Destination Gateway Flags Ref Use Interface ---------------- ---------------- ----- ----- ------ --------- 192.168.22.0 192.168.22.50 U 3 5 hme0 192.168.44.0 192.168.44.51 U 3 5 hme0 172.35.63.0 172.35.63.51 U 2 1 hme1 default 172.35.63.1 UG 3 5 127.0.0.1 127.0.0.1 UH 0 2 lo0 xenon#
To ensure that this is added whenever we boot the machine, we could add the above route command to the script named /etc/init.d/routes that we created in Chapter 11, “Connecting to the Local Area Network.” The easier and most widely used method, though, is to create a file named /etc/defaultrouter and add the IP address of the router to it:
xenon# cat /etc/defaultrouter 172.35.63.1 xenon#
At boot-time, the system will check for the existence of this file and automatically create the route for us.
Host Names or Addresses
The defaultrouter file can contain either a host name or an IP address; we have decided to use IP addresses. The reason for this is that if host names are used, the system must be able to resolve them (i.e., determine their IP address), and communicate with them early in the boot process—normally before any additional routes have been configured, which means they must be in the local hosts file. By using addresses, we are sure we won't forget to update the hosts file and cause ourselves any problems.