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⁠Chapt er 2 . Configure IP Net working
should be of the format ro ute-ifname. There are two types of commands to use in the configuration
files; ip commands as explained in Section 2.4.4.1, “ Static Routes Using the IP Command Arguments
Format” and the Network/Netmask format as explained in Section 2.4.4.2, “ Network/Netmask
D irectives Format” .
2 .4 .4 .1 . St at ic Ro ut e s Using t he IP Co m m and Argum e nt s Fo rm at
If required in a per-interface configuration file, for example /etc/sysco nfi g /netwo rkscri pts/ro ute-eth0 , define a route to a default gateway on the first line. This is only required if
the gateway is not set via D HC P and is not set globally in the /etc/sysco nfi g /netwo rk file:
default via 192.168.1.1 d ev interface
where 192.168.1.1 is the IP address of the default gateway. The interface is the interface that is
connected to, or can reach, the default gateway. The d ev option can be omitted, it is optional. Note
that this setting takes precedence over a setting in the /etc/sysco nfi g /netwo rk file.
If a route to a remote network is required, a static route can be specified as follows. Each line is
parsed as an individual route:
10.10.10.0/24 via 192.168.1.1 [d ev interface]
where 10.10.10.0/24 is the network address and prefix length of the remote or destination network. The
address 192.168.1.1 is the IP address leading to the remote network. It is preferably the next hop
address but the address of the exit interface will work. The “ next hop” means the remote end of a link,
for example a gateway or router. The d ev option can be used to specify the exit interface interface but
it is not required. Add as many static routes as required.
The following is an example of a ro ute-interface file using the ip command arguments format.
The default gateway is 19 2. 16 8. 0 . 1, interface eth0 and a leased line or WAN connection is
available at 19 2. 16 8. 0 . 10 . The two static routes are for reaching the 10 . 10 . 10 . 0 /24 network
and the 172. 16 . 1. 10 /32 host:
default via 192.168.0.1 dev eth0
10.10.10.0/24 via 192.168.0.10 dev eth0
172.16.1.10/32 via 192.168.0.10 dev eth0
In the above example, packets going to the local 19 2. 16 8. 0 . 0 /24 network will be directed out the
interface attached to that network. Packets going to the 10 . 10 . 10 . 0 /24 network and
172. 16 . 1. 10 /32 host will be directed to 19 2. 16 8. 0 . 10 . Packets to unknown, remote, networks
will use the default gateway therefore static routes should only be configured for remote networks or
hosts if the default route is not suitable. Remote in this context means any networks or hosts that are
not directly attached to the system.
Specifying an exit interface is optional. It can be useful if you want to force traffic out of a specific
interface. For example, in the case of a VPN, you can force traffic to a remote network to pass through
a tun0 interface even when the interface is in a different subnet to the destination network.
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